The Six Precious Metals Of The Platinum Group

In the periodic table of elements, six metallic elements are bunched together in the d-block, specifically in groups 8 to 9, periods 5 and 6. All transition metals, these six elements are collectively referred to as the "platinum group metals". These precious metals tend to occur with one another in mineral deposits. Likewise, they are alike in both chemical and physical properties.

In the order of their arrangement in the periodic table, the six metallic elements of the platinum group are ruthenium, rhodium, palladium, osmium, iridium, and platinum. A brief description of each of these precious metals is provided below.

1. Ruthenium - This element is represented by the symbol Ru. Its atomic number is 44. It is mostly found in platinum ores and often used in platinum alloys as a catalyst. Its two main physical characteristics refer to its hardness as a metal and to its silvery-white color. The former characteristic makes ruthenium ideal for use in making wear-resistance electrical contacts. The price of this precious metal as of January 2010 is estimated to be about USD173 per troy ounce (USD5,562 per kilogram).

2. Rhodium - This element is represented by the symbol Rh. Its atomic number is 45. Its occurrence is similar to that of ruthenium, and its primary use is as a catalytic converter. Rhodium is considered perhaps the rarest element. It is also known to be the most expensive precious metal, with a price estimated to be about USD2,750 per troy ounce (USD88,415 per kilogram) as of January 2010.

3. Palladium - This element is represented by the symbol Pd. Its atomic number is 46. It is also considered one of the rarest precious metals. Palladium closely resembles its co-member in the platinum group - platinum. It is soft and is silvery-white in color. Like rhodium, palladium is largely used as a catalytic converter. As of January 2010, the price of this metal is estimated to be approximately USD424 per troy ounce (USD13,632 per kilogram).

4. Osmium - This element is represented by the symbol Os. Its atomic number is 76. It is found in nature as an alloy in platinum ores. Osmium is considered the densest natural element. It is brittle and is blue-gray in color. Because of its hardness, osmium is alloyed with the other metals in its group and used in electrical contacts and high-quality fountain pen tips. The price of osmium, as of January 2010, is about USD32.15 per troy ounce (USD12,217 per kilogram).

5. Iridium - This element is represented by the symbol Ir. Its atomic number is 77. Like osmium, iridium is very hard and brittle; it has a different color though - silvery-white. Its principal use is for electrical purposes, mainly because of its density and its high resistance to corrosion even at extremely high temperatures. Iridium is considered the fourth least abundant element in the Earth's crust, after rhenium, ruthenium, and rhodium. Its price is estimated to be about USD408 per troy ounce (USD13,117 per kilogram) as of January 2010.

6. Platinum - This element, after which this group of precious metals is named, is represented by the symbol Pt. Its atomic number is 78. Platinum is dense, ductile, and malleable; it is gray-white in color. Known to be highly resistant to corrosion, this precious metal is used in jewelry, electrical contacts, and laboratory equipment. Its price, as of January 2010, is USD1,555 per troy ounce (USD49,995 per kilogram), making it the second most expensive precious metal, after rhodium.

Evident from the description of each of these six precious metals is that all of them have outstanding catalytic properties and high resistance to tarnish and wear. These characteristics make any of them well suited for fine jewelry. Additionally, their excellent resistance to extremely high temperatures makes them ideal for many different industrial uses.

Three Methods Of Assay For Raw Precious Metals

Items of jewelry or art made of precious metals are hallmarked based on specific requirements either of the country of import or the place of manufacture. Such items, particularly those made of silver, gold, or platinum, are struck with an official mark (or series of marks), which guarantees fineness or purity of the metal used.

To determine the precious metal content in an item, certain non-destructive assay techniques are used. Two examples are the touchstone method (a very old assay method) and the X-ray fluorescence method (the modern, non-destructive assay method). While these assay methods are suited for finished goods (again because they are non-destructive), three other methods are more suited for raw precious metals:

Titration:

This assay method is one of the most widely used laboratory technique, which involves the analysis and determination of unknown concentration of a given reactant. It is used to assay silver bullion or stock. In this method, a reagent (titrant) of a known volume and concentration is utilized to react with a solution of the substance being analyzed (titrand), whose concentration is unknown.

With the use of an instrument called burette (to add the titrant), the exact consumed amount, on reaching the endpoint, can be determined. The endpoint refers to the point at which the assay is complete. The completion is signaled by an indicator. There are at least four types of titration. These are acid-base, redox, complexometric, and Zeta potential.

Cupellation:

This technique is considered the most exact, elaborate, and destructive method of assay and is best suited for gold bullion or stock. Also called fire assay, the method involves treating ores or alloyed metals under high temperatures and carefully controlled operations to separate gold from base metals (copper, zinc, or lead), which may be present in the ore. Once the base metals are heated at high temperatures, the gold (as well as the other precious metals that may be present) remains apart and the other non-precious metals react forming other compounds. Cupellation basically has two processes: large scale and small scale.

Spectrometry:

This method is best used to assay platinum bullion or stock. With the use of a spectrometer or spectrograph, the amount or concentration of a given substance is assessed. The substances are identified through the spectrum they absorb or emit. This assay method has several types. These include absorption, fluorescence, X-ray, flame, visible, ultraviolet, infrared, photoemission, Mossbauer, nuclear magnetic resonance, and Raman.

Again, the X-ray fluorescence (XRF) method is the modern assay method widely used today for analyzing precious metals, including (besides silver, gold, and platinum) rhenium, ruthenium, iridium, and palladium. As a non-destructive assay method, XRF can identify various elements in a substance (in fact, even in powder and liquid ones) within a few minutes.

One of the most important aspects in any of the assay methods pertains to the accurate determination of the composition of a substance at various points in the process. Controlling and minimizing metal losses can only be achieved through close monitoring of the composition of the work in progress.

Precious Metals: A Brief Description Of The Four Platinum Bullion Coins

Bullion coins are coins made from precious metals. Their market values are determined by their inherent precious metal contents. As such bullion coins are mainly kept as investments or stores of value.

Most of the bullion coins available are made from silver or gold. A few also come in platinum though, including the American Platinum Eagle, the Canadian Platinum Maple Leaf, the Australian Platinum Koala, and the Manx Noble. Here's a quick rundown of each of these four platinum bullion coins:

The American Platinum Eagle:

The American Platinum Eagle bullion coins were first minted and released in 1997 by the United States Mint. They are offered in four varieties:

1. 1/10 ounce (oz.) coin - With a face value of USD10, 3.112 grams (g) in weight, 0.95 millimeters (mm) thick, and 16.5 mm in diameter.

2. 1/4 oz. coin - With a face value of USD25, 7.78 g in weight, 1.32 mm thick, and 22 mm in diameter.

3. 1/2 oz. coin - With a face value of USD50, 15.56 g in weight, 1.75 mm thick, and 27 mm in diameter.

4. 1 oz. coin - With a face value of USD100, 31.12 g in weight, 2.39 mm thick, and 32.7 mm in diameter.

All coin varieties consist of 0.9995 fine platinum. One interesting feature of the American Platinum Eagle coin is that its reverse design changes every year.

The Canadian Platinum Maple Leaf:

The Canadian Platinum Maple Leaf bullion coins were issued from 1988 until 2002 by the Royal Canadian Mint (RCM). They were offered in four varieties: 1/10 oz. coin (with a face value (FV) of CD5), 1/4 oz. coin (FV: CD10), 1/2 oz. coin (FV: CD20), and 1 oz. coin (FV: CD50).

Two additional varieties, 1/20 oz. coin (FV: CD1) and 1/15 oz. coin (FV: CD2), were issued by RCM, but only in 1994. In 2009, the 1 oz. coin was reintroduced. All coins, which have legal tender status in Canada, consist of 0.9995 pure platinum.

The Australian Platinum Koala:

The Australian Platinum Koala bullion coins were first released in 1988 by the Perth Mint, the oldest currently operating mint in Australia. The coin comes in 1 oz. variety, with a face value of AD100. As with most other bullion coins, this value is much lower than the coin's bullion value.

On the coin's obverse is a koala, in sunken relief (i.e., lowered from the coin's plane); on the reverse is Queen Elizabeth II. The coin has legal tender status in Australia.

The Manx Noble:

The Manx Noble platinum bullion coins were minted from 1983 to 1989 by the Pobjoy Mint, the leading private mint in Europe. The coins were offered in five varieties:

1. 1/20 oz. coin - With 1.555 g platinum content, 1.556 g in weight, and 13.9 mm in diameter.

2. 1/10 ounce coin - With 3.11 g platinum content, 3.112 g in weight, and 16.5 mm in diameter.

3. 1/4 ounce coin - With 7.776 g platinum content, 7.78 g in weight, and 22 mm in diameter.

4. 1/2 ounce coin - With 15.552 g platinum content, 15.6 g in weight, and 27 mm in diameter.

5. 1 ounce coin - With 31.103 g platinum content, 31.119 g in weight, and 32.7 mm in diameter.

The coins have no currency value. Their value, rather, is equal to their respective platinum contents. All coins consist of 0.9995 pure platinum.

On the coin's obverse is Queen Elizabeth II, along with these texts: "ISLE OF MAN" and "ELIZABETH II". On the reverse are a Viking ship, the denomination, platinum content, and the words "Platinum fine".

The Eight Precious Metals Considered Noble Metals

Most metallic chemical elements are known to easily oxidize and corrode, especially at high temperatures. Metals that have excellent resistance to oxidation and corrosion, even at high temperatures, are called noble metals. While there is no strict definition for this group of metals, it usually includes those that are extremely rare.

Thus, metals that are labeled "precious" are also considered noble metals (note, however, that noble metals are not necessarily precious metals). There are nine known precious metals - gold, platinum, iridium, palladium, osmium, silver, rhodium, ruthenium, and rhenium. With the exception of the latter, all are considered noble metals.

Using the "aqua regia" test (aqua regia is a mixture of concentrated nitric acid and concentrated hydrochloric acid, which is highly corrosive), here's how the eight precious-noble metals react:

• Gold, platinum, palladium, and osmium dissolve.

• Ruthenium dissolves only in the presence of oxygen.

• Rhodium dissolves only when it is in a fine, pulverized form.

• Iridium and silver do not dissolve under any condition.

In another definition, noble metals may refer to electrically conductive elements. Here, the term "noble" serves as a modifying word, such that the electrical conductivity of materials is graded from noble to active. Using this definition for noble metals then, we will find that silver is less noble than, say, graphite (although graphite is an elemental form of carbon and, therefore, is not considered a metal).

Below is a comparison of the chemical nobility of the precious metals (again, excluding rhenium), with details of their specific electronic configurations, simplified reactions (as per the pH diagram), and electrode potentials. The list is presented in order of increasing atomic number.

1. Ruthenium - VIIIb/5; Ru -> Ru2+ + 2 e-; 0.455 V

2. Rhodium - VIIIb/5; Rh -> Rh2+ + 2 e-; 0.600 V

3. Palladium - VIIIb/5; Pd -> Pd2+ + 2 e-; 0.987 V

4. Silver - Ib/5; Ag -> Ag+ + e-; 0.7996 V

5. Osmium - VIIIb/6; Os + 4 H2O -> OsO4 + 8 H+ + 8 e-; 0.838 V

6. Iridium - VIIIb/6; Ir -> Ir3+ + 3 e-; 1.156 V

7. Platinum - VIIIb/6; Pt -> Pt2+ + 2 e-; 1.18 V

8. Gold - Ib/6; Au -> Au3+ + 3 e-; 1.498 V

The second item appearing after the name of the metal (the three items are separated by semi-colons) represents the metal's reaction in water. In the pH diagram, the pH symbol is labeled on the horizontal axis to signify the -log function of the concentration of H+ ion. The lines, which represent equilibrium for the concentration, are drawn for ions at unit activity. Other concentrations may be represented by additional lines. The voltage potential is represented by a vertical axis, which is labeled Eh, where "h" stands for hydrogen.

Physics has an even more strict definition for noble metals. Here, it is required that the electronic structure's d-bands are filled. If this definition is followed, only gold and silver (among the precious metals) qualify as noble metals. Also note that the varying reactivity of the precious metals can readily be observed while preparing their surfaces in the vacuum regime called ultra high vacuum.

Precious Metals: Silver As An Investment:

Silver is like three other precious metals (gold, palladium, and platinum) in terms of being regarded as an investment commodity. In fact, this precious metal has been regarded as a form of currency and a store of value for over four centuries.

There are different ways by which one may invest in silver. Six are presented here:

Buying silver coins:

This is a popular way of taking hold of silver - physically. Perhaps the best example of a silver coin is the Canadian Silver Maple Leaf, which consists of 99.99% pure silver. Silver coins may either be "fine silver" or "junk silver". Junk silver coins are older coins with a lower percentage of silver. Examples of these are the dime, quarter, and fifty-cent U.S. coins minted in 1964 or earlier. These coins contain 90% silver and are 8/10 troy ounce per 1 USD of face value.

Buying silver bullion bars:

This is the most traditional way of investing in silver. Silver bullion bars can be bought or sold over the counter in most banks in Switzerland. They may be stored in safe deposit boxes in banks or placed in non-fungible (allocated) or pooled (unallocated) storage with a silver dealer.

Opening a silver account:

An investor may open a silver account with one of the major banks in Switzerland. Here, silver can be bought or sold over the counter just like any foreign currency. However, the bank client does not own the actual silver metal. Instead, he/she has a claim against the bank for a specified quantity of the metal. A silver account is backed through either allocated or unallocated storage.

Owning a silver certificate:

In lieu of storing actual silver bullion, an investor may opt for ownership of a silver certificate. A silver certificate allows an investor to buy and sell the security sans the inconveniences associated with the physical silver's transfer. The Perth Mint Certificate Programme, which is fully guaranteed by the Government of Western Australia, is the only silver certificate program in the world that is guaranteed by a national government.

Trading in Exchange-Traded Funds (ETFs):

An investor can have an easy way of gaining exposure to the price of silver through an ETF. Some of the well-known ETFs include iShares Silver Trust (with ticker symbol NYSE: SLV), Central Fund of Canada (with ticker symbols TSX: CEF.NV.A, NYSE: CEF), and ETFS Silver Trust (with ticker symbol NYSE: SIVR). Trading in ETFs means doing away with the inconveniences associated with the handling of physical silver bars.

Entering in a Contract For Difference (CFD):

Some of the noted financial services firms, especially those in the United Kingdom, provide Contract for Difference (CFD). In this silver investment vehicle, two parties (a "buyer" and a "seller") enter into a contract, in which the seller agrees to pay the buyer the difference between the current value of silver and its value at contract time. In case the difference is negative, the seller receives payment instead from the buyer. A CFD, therefore, allows an investor to take advantage of long or short positions, enabling him/her to speculate on these markets.

It must be mentioned here though that silver has lost its forced tender status in the United States since the abandonment of the silver standard, when, on August 15, 1967, then U.S. President Lyndon B. Johnson announced that the U.S. would discontinue redeeming currency for silver (or any other precious metal).

Silver: Precious Metal With The Highest Thermal And Electrical Conductivity

Silver is generally described as a soft, white, lustrous metallic chemical element. It occurs naturally in its pure form, as an alloy with other metallic elements (especially gold), and in chlorargyrite and other minerals. As one of three coinage metals (the other two being copper and gold), silver is very malleable and ductile.

Of the different metals, silver is known to have the highest thermal conductivity. Similarly of the different known elements, silver has the highest electrical conductivity. Provided below are some of the properties of this precious metal.

General:

• Chemical Symbol: Ag

• Atomic Number: 47

• Category (as an element): Transition Metal

• Group/ Period/ Block (in the Periodic Table): 11/ 5/ d

• Atomic Weight: 107.8682 g.mol-1

• Electron Configuration: [Kr] 4d10 5s1

Physical:

• Density (near room temperature): 10.49 g.cm-3

• Liquid Density (at melting point): 9.320 g.cm-3

• Melting Point: 961.78°C, 1234.93°F, 2041.4°K

• Boiling Point: 2162°C, 3924°F, 2435°K

• Heat of Fusion: 11.28 kJ.mol-1

• Heat of Vaporization: 250.58 kJ.mol-1

Atomic:

• Oxidation States: 1, 2, 3

• Electronegativity: 1.93 (Pauling scale)

• Atomic Radius: 144 picometre

• Covalent Radius: 145±5 picometre

• Van der Waals Radius: 172 picometre

• Ionization Energies: 731 kJ.mol-1 (first), 2070 kJ.mol-1 (second), 3361 kJ.mol-1 (third)

Despite having higher electrical conductivity than copper, silver isn't as much used for electrical purposes as copper is. There are two reasons for this: first is that silver has a greater tendency to tarnish; and second is that silver is much more expensive.

As a precious metal, silver has been much valued for ages with its so many applications, as in the following:

1. Jewelry (sterling silver is used in making fine jewelry and watches).

2. Silverware (sterling silver is also used in making utensils, tableware and ornaments).

3. Photography (silver nitrate and silver halides are used in making films).

4. Electrical and electronic products (silver paints are used in making printed circuits; silver electrical contacts are used in making computer keyboards).

5. Dentistry (silver-mercury alloy is used in making dental amalgams).

6. Optics and mirrors.

7. Various industrial and commercial uses (silver is ideal for use as a catalyst in chemical reactions).

8. Clothing (silver ions are mixed with the polymer to make yarns).

9. Medicine (silver compounds and silver ions have toxic effect on some viruses, fungi and bacteria, but not on humans).

10. Currency or coinage (as in silver bullion).

The principal sources of silver are copper, lead, zinc and gold ores. It also occurs in the minerals chlorargyrite and argentite. Of course, silver occurs natively, too. Some of the top silver-producing countries in the world are the United States, Canada, Peru, and Mexico. Fine silver, which has no less than 99.9% silver, is available commercially.

Because of competing store-of-value and industrial demands, the price of silver has fluctuated considerably over the last century. As of the beginning of 2010, the price of this precious metal is estimated at about 18 U.S. dollars per troy ounce (or 588 U.S. dollars per kilogram).

Safety Issues Concerning Precious Metals

The metallic chemical elements collectively known as precious metals are called as such because of their extreme rarity and high economic value. Precious metals occur naturally or are by-products of the processing of other less rare metals.

In order of increasing mass abundance (parts per billion), the precious metals are rhenium, rhodium, iridium, ruthenium, osmium, gold, platinum, palladium, and silver. These metals are not radioactive and are mostly used for industrial purposes and for jewelry.

Still, precious metals have some safety issues attached to them:

Rhenium:

Since rhenium is used in very small amounts, its toxicity is virtually unknown. The hazardous property of rhenium halide, for example, may be attributed either to rhenium itself or to the other elements that make up the compound. Another rhenium compound - potassium perrhenate - is known to have a median lethal dose much like that of sodium chloride (commonly known as table salt).

Rhodium:

Although rhodium is inert (being a noble metal, as almost all the other precious metals are), it can be reactive, especially if used as compounds. In its basic form, however, rhodium is not known to cause any harm.

Iridium:

Iridium, when finely divided, can pose some hazards - it can ignite in air. Apart from this, accidental exposure to a radioisotope of iridium may cause poisoning by radiation, burns, and even death.

Ruthenium:

Three conditions may be associated with exposure to ruthenium: it can stain the skin; it may accumulate in bones; and it may increase the risk of cancer. Ruthenium tetroxide, a yellow, diamagnetic tetrahedral ruthenium compound, is highly toxic and volatile; it may explode if it comes into contact with combustible materials.

Osmium:

Osmium, like iridium, can ignite spontaneously in air when in finely divided form. The compound osmium tetroxide, in particular, is highly volatile and is extremely toxic if accidentally inhaled, ingested, or comes into contact with the skin.

Gold:

Gold, in its elemental form, does not cause irritation and is not toxic even when ingested. In fact, it is used as a component in some alcoholic drinks and as a food additive. However, ionic chemical compounds of gold (example, gold chloride) can be extremely harmful to the kidneys and liver.

Platinum:

Findings by the U.S. federal agency CDC reveal that exposure to platinum salts, on the short term, may cause nose, throat, and eye irritation. Long-term exposure to these compounds, on the other hand, may cause skin and respiratory allergies.

Palladium:

Palladium in bulk metallic form is completely inert. The same can't be said though of the metal in finely divided form, which can readily ignite in air.

Silver:

Silver compounds (example, colloidal silver), when absorbed into the body, may cause argyria, a condition characterized by the bluish-gray pigmentation of the skin, mucous tissues, and the eyes. While the condition is not really harmful to one's health, it is often permanent. Otherwise, silver per se is not at all toxic.

It certainly is important to know that each of the precious metals has possible health hazards so that first-time handlers can take the necessary precautions.

Ruthenium: Most Versatile Of The Platinum Group of Precious Metals

Arranged by name alphabetically, ruthenium is the last of six metallic elements in the platinum group. This precious metal is characterized as being both polyvalent and versatile. In fact, it is known to be more versatile than any of the other five precious metals in the platinum group.

A hard, white metal, ruthenium is known to have four crystal modifications. While it does not tarnish under normal temperature, it does oxidize readily when exposed to air. It can be plated by means of two methods: thermal decomposition and electrodeposition.

Following is a list of some of the properties of ruthenium:

General:

• Chemical Symbol: Ru

• Atomic Number: 44

• Category (as an element): Transition Metal

• Group/ Period/ Block (in the Periodic Table): 8/ 5/ d

• Atomic Weight: 101.07 g.mol-1

• Electron Configuration: [Kr] 4d7 5s1

Physical:

• Density (near room temperature): 12.45 g.cm-3

• Liquid Density (at melting point): 10.65 g.cm-3

• Melting Point: 2334°C, 4233°F, 2607.4°K

• Boiling Point: 4150°C, 7502°F, 4423°K

• Heat of Fusion: 38.59 kJ.mol-1

• Heat of Vaporization: 591.6 kJ.mol-1

Atomic:

• Oxidation States: 8, 7, 6, 4, 3, 2, 1, -2

• Electronegativity: 2.3 (Pauling scale)

• Atomic Radius: 134 picometre

• Covalent Radius: 146±7 picometre

• Ionization Energies: 710.2 kJ.mol-1 (first), 1620 kJ.mol-1 (second), 2747 kJ.mol-1 (third)

Ruthenium-palladium and ruthenium-platinum alloys are used in making electrical contacts for wear resistance. As a matter of fact, ruthenium is a very effective hardener for both palladium and platinum. When a small amount of ruthenium is added to titanium, the latter's corrosion resistance is improved significantly.

As to its other applications, ruthenium is used in:

1. film chip resistors;

2. jewelry (when alloyed with gold);

3. high-temperature superalloys (used in making the turbine blades in jet engines);

4. fountain pen nibs;

5. removing hydrogen sulfide from various industrial processes;

6. electrolytic cells for various chemical processes (as a component of mixed-metal oxide anodes);

7. optical sensor device;

8. radiotherapy (particularly of eye tumors).

Along with the five other precious metals in the platinum group, ruthenium is generally found in ores in North America, South America, and the Ural Mountains in Russia. Small quantities of this element also occur in pentlandite (an iron-nickel sulfide) obtained from Sudbury in Ontario, Canada, and in South Africa's pyroxenite (an ultrabasic igneous rock) deposits.

Commercially, ruthenium is obtained as a by-product from copper and nickel processing (as how all the other platinum group metals are obtained), although it is likewise obtainable through direct processing of platinoid ores. It is isolated by means of a complex chemical process. The process involves reduction of ammonium ruthenium chloride with the use of hydrogen. This yields a powder which, in turn, is consolidated by means of a technique called argon-arc welding.

In terms of abundance in the Earth's crust, ruthenium ranks 74th among all the different known elements or metals and is, therefore, one of the rarest. Estimates place world reserves at 5,000 tonnes, and annual mining output about 12 tonnes. Ruthenium's price is estimated to be approximately 1,000 U.S. dollars per troy ounce.

Rhodium: Costliest Precious Metal

In 1803, the English physicist and chemist William Hyde Wollaston discovered a chemical element that is today considered the most expensive of the precious metals. This precious metal, which belongs to the platinum group metals, is rhodium. With its current price of around 1,000 U.S. dollars per troy ounce, rhodium is about five times costlier than platinum.

Wollaston's discovery of rhodium was made possible with the use of crude platinum ore. He first dissolved the ore in nitro-hydrochloric acid (also called aqua regia) and neutralized the acid with lye (or sodium hydroxide). By adding salmiac (ammonium chloride), he then precipitated the platinum. All other metals, including rhodium, were precipitated with zinc. Rhodium was further precipitated by the addition of sodium chloride. Finally, it was washed with ethanol and reacted with zinc, forming the precious metal that it is known today.

Since rhodium occurs in ores mixed with other metals (examples: silver, gold, and platinum), its extraction is complex. For example, it is obtained as a white inert metal from platinum ores, which is quite difficult to fuse. The main source of this precious metal is in South Africa, which accounts for about 80 percent of the total world exports. Estimates place the annual production of rhodium at only about 25 tons.

Some of the properties of rhodium are listed below.

General:

• Chemical Symbol: Rh

• Atomic Number: 45

• Category (as an element): Transition Metal

• Group/ Period/ Block (in the Periodic Table): 9/ 5/ d

• Atomic Weight: 102.90550 g.mol-1

• Electron Configuration: [Kr] 4d8 5s1

Physical:

• Density (near room temperature): 12.41 g.cm-3

• Liquid Density (at melting point): 10.7 g.cm-3

• Melting Point: 1964°C, 3567°F, 2237°K

• Boiling Point: 3695°C, 6683°F, 3968°K

• Heat of Fusion: 26.59 kJ.mol-1

• Heat of Vaporization: 494 kJ.mol-1

Atomic:

• Oxidation States: 6, 5, 4, 3, 2, 1, -1

• Electronegativity: 2.28 (Pauling scale)

• Atomic Radius: 134 picometre

• Covalent Radius: 142±7 picometre

• Ionization Energies: 719.7 kJ.mol-1 (first), 1740 kJ.mol-1 (second), 2997 kJ.mol-1 (third)

The principal use of rhodium is as a catalytic converter in automotive vehicles, which reduces the toxicity of engine emissions by converting these into less harmful gases. Rhodium is likewise used in jewelry, such as when it is electroplated on platinum, sterling silver, or white gold (called rhodium flashing) to strengthen the metal or give it a reflective surface.

Rhodium has at least five other uses or applications:

1. As an alloying agent, to improve platinum's resistance to corrosion.

2. For optical instruments.

3. As an electrical contact material (because of its stable resistance to contact and low resistance to electricity).

4. As a filter in X-ray systems (such as mammography).

5. In surfaces of high quality pens (because of its high mechanical and chemical resistance).

Obviously because of its extremely high price, rhodium signifies wealth. In some cases, it has been used in awards or recognitions, such as when the Guinness Book of World Records handed out a rhodium-plated disc to Paul McCartney in 1979, in recognition of his being the all-time best-selling recording artist and songwriter in history.

Rhenium: Last Naturally Occurring Stable Precious Metal Discovered

In the periodic table of elements, rhenium is found as a third-row transition metal in group 7. Known to be one of the rarest precious metals in the Earth's crust, rhenium has an average concentration of 1 part per billion. It is obtained mainly as a by-product of the refinement of two other chemical elements - copper and molybdenum.

Rhenium was discovered as a trace element in the mineral columbite and in platinum ores. Three German chemists - Otto Berg and the couple Walter Noddack and Ida Tacke - made the discovery in 1925. This find made rhenium the last identified naturally occurring precious metal with stable isotopes. Actually, naturally occurring rhenium is composed of 2 stable isotopes and 26 unstable ones.

Following is a list of some of the properties of rhenium:

General:

• Chemical Symbol: Re

• Atomic Number: 75

• Category (as an element): Transition Metal

• Group/ Period/ Block (in the Periodic Table): 7/ 6/ d

• Atomic Weight: 186.207 g.mol-1

• Electron Configuration: [Xe] 4f14 5d5 6s2

Physical:

• Density (near room temperature): 21.02 g.cm-3

• Liquid Density (at melting point): 18.9 g.cm-3

• Melting Point: 3186°C, 5767°F, 3459°K

• Boiling Point: 5596°C, 10105°F, 5869°K

• Heat of Fusion: 60.43 kJ.mol-1

• Heat of Vaporization: 704 kJ.mol-1

Atomic:

• Oxidation States: 7, 6, 5, 4, 3, 2, 1, 0, -1

• Electronegativity: 1.9 (Pauling scale)

• Atomic Radius: 137 picometre

• Covalent Radius: 151±7 picometre

• Ionization Energies: 760 kJ.mol-1 (first), 1260 kJ.mol-1 (second), 2510 kJ.mol-1 (third)

Rhenium is silvery-white in appearance. It is the third element (after tungsten and carbon) with the highest melting point and the fourth densest (after platinum, iridium, and osmium). Commercially, rhenium is traded in powder form. Its principal application is in the making of certain parts of jet engines. Here, the metal is added to high-temperature nickel-based superalloys.

Other uses of rhenium are as follows:

1. As catalysts in making lead-free, high-octane gasoline.

2. As filaments in making ion gauges, mass spectrographs, and photoflash lamps.

3. As electrical contact materials, due to its high resistance to arc corrosion and wear.

4. As catalysts for hydrogenation of fine chemicals, because of its high resistance to chemical poisoning from phosphorus, sulfur, and nitrogen.

5. As treatment for liver cancer, because of its radioactive isotopes.

Rhenium resources are identified in several countries, which include Chile, Peru, Armenia, Mexico, Russia, Canada, Kazakhstan, and Uzbekistan. The estimated total resource from these eight countries is 6,000 tonnes (6 million kilograms).

The United States alone, on the other hand, has an estimated total resource of 5,000 tonnes (5 million kilograms). These are identified in the states of Arizona, Miami, and Utah. But in spite of these significant resources, the U.S. continues to import a big part of its total consumption of the precious metal from some of the countries mentioned above.

Since rhenium and its compounds are used in very small amounts, very little is known about their toxicity. So far, only a few rhenium compounds have been tested for toxicity, and these include rhenium trichloride and potassium perrhenate.

The price of rhenium is about 250 U.S. dollars per troy ounce (about 8,300 U.S. dollars per kilogram).

Precious Metals Discoverers And Name Etymologies

The group of precious metals consists of two coinage metals, six platinum group metals, and one metal considered the last naturally occurring stable element to be discovered. Except for gold and silver (the two coinage metals), the rest of the precious metals have recorded discoveries.

In the following list, the names of the discoverers and name etymologies of the seven precious metals (again, those with recorded discoveries) are provided. The year of discovery of each of these elements, as presented here, refers to the year when the element was first identified as the pure element. Also provided are their respective name etymologies.

1. Platinum - Antonio de Ulloa, a Spanish explorer and astronomer, is generally credited with the modern rediscovery (in 1735) of platinum. This precious metal actually was first described in 1557 by Giulio Cesare della Scala, an Italian physician. Because it was first chanced upon in silver mine in South America, platinum was named as such, after the Spanish word "platina", which translates to "little silver".

2. Palladium - William Hyde Wollaston, an English chemist and physicist, discovered palladium in 1803 in samples of platinum ore obtained from South America. He named it after the asteroid Pallas, which was discovered on March 28 the year before.

3. Osmium - Smithson Tennant, an English chemist, discovered osmium in 1803 from the residues of platinum ores that were dissolved in nitro-hydrochloric acid. Osmium's characteristic of having a bad smell led to its naming as such, which was derived from the Greek word "osme", meaning "smell".

4. Iridium - Smithson Tennant discovered iridium in 1803, at the same time of his discovery of osmium from the same solution of platinum ores. Iridium is named after the Latin word "iris", which means "rainbow".

5. Rhodium - William Hyde Wollaston discovered rhodium in 1803, shortly after he discovered palladium. He discovered this precious metal from crude platinum samples obtained from South America. The name rhodium was derived from the Greek word "rhodon", which means "rose".

6. Ruthenium - Karl Karlovich Klaus, a Russian chemist and naturalist, is usually credited with the discovery of ruthenium (in 1844). He discovered it from platinum ore samples he obtained from the Ural Mountains in Russia. He named this precious metal after "ruthenia", the Latin word for Klaus's home country Russia.

7. Rhenium - A team of German chemists, composed of Walter Noddack, Ida Tacke, and Otto Carl Berg, discovered rhenium in 1925. They discovered the element from platinum ore samples as well as from the mineral gadolinite. They named it after the Latin word "rhenus", for "Rhine", one of Europe's longest and most important rivers.

As for the precious metals gold and silver, both are known to be already in use since ancient times (gold was in use probably as early as before 6000 BC, while silver probably as early as before 5000 BC). The name "gold" was derived from the same Anglo-Saxon word, which translates to "bright yellow". The name "silver", on the other hand, is from "seolfor", also an Anglo-Saxon word.

Precious Metal Determinants: Rarity And High Economic Value

A metal is considered "precious" if it is rare and is of high economic value. Under these two factors, nine metallic chemical elements qualify as precious metals. These are, in no particular order, gold, palladium, silver, rhodium, iridium, ruthenium, platinum, osmium, and rhenium.

So that while the chemical element tellurium is considered one of the rarest element in the Earth's crust (its mass abundance being the same as that of rhodium, iridium, and ruthenium), its estimated price is only less than 5 U.S. dollars per troy ounce, and, therefore, cannot be considered a precious metal. The same can be said of bismuth, which has a mass abundance half less than that of palladium, but with a price of only a little more than a tenth of tellurium's price.

In terms of mass abundance, expressed in parts per billion (ppb), here's how the nine precious metals are ranked (rare to rarest): 9th: silver (75 ppb); 8th: palladium (15 ppb); 7th: gold (4 ppb); 6th: osmium (1.5 ppb); 5th to 3rd: iridium, rhodium, and ruthenium (1 ppb); 2nd: rhenium (0.7 ppb); and 1st: platinum (0.003 ppb).

The ranking appears different when the estimated world market prices, per troy ounce, of these nine precious metals are considered (estimates as of January 2010):

1st: Rhodium - USD2,750

2nd: Platinum - USD1,555

3rd: Gold - USD1,131

4th: Palladium - USD424

5th: Iridium - USD408

6th: Osmium - USD380

7th: Rhenium - USD194

8th: Ruthenium - USD173

9th: Silver - USD18

Of the nine precious metals, gold and silver are the best known. Apart from being traditional coinage metals (along with copper), both gold and silver are also well known for their uses in jewelry and art; they likewise have certain industrial uses.

A third important factor that will qualify an element as a precious metal, as may be noted from the uses of gold and silver above, is that it should not be radioactive. Thus, the chemical elements actinium, polonium, and radium are not considered precious metals because they are highly radioactive.

Compared to most other elements, precious metals are chemically less reactive, have higher melting points, and are more ductile - properties that make them ideal for many commercial and industrial applications.

In earlier times, precious metals were mainly used as currency. Today, however, they are highly regarded as investment and industrial commodities. Four of them, in fact - silver, gold, platinum, and palladium -, are minted into coins or cast into ingots and traded on commodity markets. All four are assigned the ISO 4217 currency code.

Hence, the role of precious metals as investments, on top of their practical use, drives the demand for them. For thousands of years, precious metals have demanded prices that are much higher than those of common industrial metals, such as nickel (about 36 cents per troy ounce) and copper (about 11 cents per troy ounce). As a matter of fact, there have been significant increases in the prices of precious metals at the turn of the Twenty-First century. This has encouraged many enterprises to go into precious metal recycling.

Platinum: Most Widely Traded Of The Platinum Group of Precious Metals

In the periodic table of the chemical elements, six metallic elements - all transition metals - are clustered together and lie in the d-block (the d-block in the periodic table refers to groups 8, 9, and 10, periods 5 and 6). These six elements are collectively referred to as the platinum group metals.

Of this group of metals, platinum is considered the most widely traded, as it is extensively used in the following: catalytic converters; dental alloys and other dentistry equipment; electrical conductors; resistive thermal devices, laboratory dishes and such other equipment capable of resisting chemical attack even in high temperature; and, of course, jewelry.

As a transition element, platinum is gray-white in appearance. Often because of this, it is mistaken for silver. Its other physical characteristics include its being malleable, ductile, and dense. But while platinum is generally resistant to corrosion, it is corroded by certain elements, such as cyanides (potassium cyanide or sodium cyanide), caustic alkalis, sulfur, and any of the five halogens (astatine, bromine, chlorine, fluorine, and iodine).

The following lists some of the properties of platinum:

General:

* Chemical Symbol: Pt

* Atomic Number: 78

* Category (as an element): Transition Metal

* Group/ Period/ Block (in the Periodic Table): 10/ 6/ d

* Atomic Weight: 195.084 g.mol-1

* Electron Configuration: [Xe] 4f14 5d9 6s1

Physical:

* Density (near room temperature): 21.45 g.cm-3

* Liquid Density (at melting point): 19.77 g.cm-3

* Melting Point: 1768.3°C, 3214.9°F, 2041.4°K

* Boiling Point: 3825°C, 6917°F, 4098°K

* Heat of Fusion: 22.17 kJ.mol-1

* Heat of Vaporization: 469 kJ.mol-1

Atomic:

* Oxidation States: 6, 5, 4, 3, 2, 1, -1, -2

* Electronegativity: 2.28 (Pauling scale)

* Atomic Radius: 139 picometre

* Covalent Radius: 136±5 picometre

* Van der Waals Radius: 175 picometre

* Ionization Energies: 870 kJ.mol-1 (first), 1791 kJ.mol-1 (second)

Platinum is known to occur as only three thousandth parts-per notation (0.003 ppm) in the Earth's crust. This makes it an extremely rare metal.

Compared to gold, platinum is more precious, although its price is considered more volatile. One of the reasons for this is that its demand is driven by industrial uses or applications. For example, its price tends to be double that of gold's when world economy is stable, but significantly goes down in times of economic uncertainty.

Because it's wear-resistant and does not tarnish, platinum is highly valued by jewelers, especially watchmakers. In 2008, its price went up to as high as 2,252 U.S. dollars per troy ounce.

Being rare and, therefore, very precious, platinum has been made synonymous to things that are considered "of the highest quality". We hear for instance of a platinum debit card holder enjoying a wide range of privileges; or of a platinum award being handed out to a music album that has sold over a million copies.

Platinum's rarity and preciousness has been so pronounced in fact as early as the Eighteenth century, that then French King Louis XV even made a declaration making platinum "the only metal fit for a king".

Placer Mining: Three Methods Used To Mine Placer Precious Metal Gold

The word placer, as will be found throughout here, is derived from the same Spanish word which means "sandbank". It specifically refers to an alluvial deposit of detrital material, such as gravel, which contains particles of precious chemical elements.

The term "placer gold", therefore, refers to gold that has formed in rocks moved and placed on stream beds by some geological forces and by the action of water. Lode gold tends to erode from its source, distributing itself naturally among other rocks that have been subjected to similar geological forces. This results to the formation of a secondary deposit.

Thus the mining of alluvial deposits for gold and other precious metal deposits is called "placer mining". Placer mining may be done through a number of tunneling procedures into riverbeds. There also are the open-cast mining and hydraulic mining. In the former, placer mining is done by open-pit; in the latter, water pressure is used for excavation.

There are three placer mining methods used to mine placer gold:

Gold Panning:

This method, which involves the use of a pan, is the oldest and simplest way to extract gold from a placer deposit. In this method, mined ore is placed in a large pan (made either of plastic or metal) and poured with a liberal amount of water; it is then agitated. The gold particles, having higher density than the other materials (examples, mud, sand and gravel; also, gold is about nineteen times heavier than water), settle to the bottom of the pan, while the lighter materials are washed over the side.

Sluice Box:

This method uses the same principle as that in gold panning, only on a larger scale. In this method, a short sluice box is used. The box is constructed with barriers along its bottom, so that the gold particles are trapped as all materials are washed by water. The sluice box method is best suited for excavation in which certain implements, such as shovels, are used to feed ore into the box.

Trommel:

This method involves the use of a screened cylinder to separate materials by size (trommel is Dutch word for "drum"). A trommel specifically consists of a rotating metal tube that is slightly tilted, with a screen at the discharge end. Attached to the inside part of the metal tube are lifter bars. Ore is fed into the trommel through its elevated end. Pressurized water is supplied to the tube and the screen sections. Valuable minerals from the ore are separated by the combination of water and mechanical action. The small pieces of ore bearing the valuable minerals pass through the screen and are concentrated further in sluices. The larger ones (those that do not pass through the screen) are moved to a waste stack using a conveyor.

Today, placer mining goes on in many parts of the world as a source of gems and industrial metals and minerals. This is true in countries like Sri Lanka and Myanmar. Placer mining for placer gold continues in British Columbia, the Yukon, and especially in Alaska.

Palladium And Platinum As Investment Precious Metals Commodities

Palladium and platinum are two of nine metallic chemical elements considered "precious" for their rarity and high economic value. Like all the other precious metals, palladium and platinum have various industrial uses. But apart from these, both are also regarded as investment commodities.

Palladium as an investment commodity:

Palladium is valued at around US$415 per troy ounce. Actually, this is much lower than its price of more than one thousand U.S. dollars per troy ounce in early 2001, when the automobile industry placed a high demand for the precious metal for use as catalytic converters.

As an investment commodity, palladium may be bought in forms of bullion coins or bars. Palladium bullion coins are internationally recognized forms of currency and have the ISO codes XPD and 964. The first known palladium coins to be issued were those of Sierra Leone in 1966. The following year, Tonga started issuing theirs.

Other countries later began issuing their own palladium bullion coins, including Canada (with its Big & Little Bear Constellations and the very popular Palladium Maple Leaf), Australia, France, China, Portugal, and the former Soviet Union. The latter, in fact, is known to have minted the most number of palladium coins in the world.

Because of low circulation of palladium coins, palladium as an investment commodity is not as good as either silver or gold. Another reason for this is the relatively wider spread between the metal's buying and selling prices.

Palladium is traded on the London Stock Exchange as an exchange-traded fund (ETF), under the ticker symbol LSE: PHPD.

Platinum as an investment commodity:

As of January 2010, platinum is valued at around us$1,555 per troy ounce (a couple years earlier, its price is about 48% higher than this - considered its peak price). Compared with silver or gold, platinum tends to trade at a higher per-unit price because it is scarcer and has lower mine output. The average mine production of platinum is 5 million troy ounces per year. This is lower by about 77 million troy ounces when compared with the annual mine production of gold, and even much lower - by about 547 million troy ounces - when compared with the yearly silver mine production.

Platinum is traded on the London Stock Exchange (as ETF, under the ticker symbol LSE: PHPT) and on the New York Mercantile Exchange. One way of investing in platinum is through platinum ingots. Platinum ingots are first assayed and hallmarked before being sold on commodity markets.

Another way of investing in platinum is through platinum coins. Platinum coins are internationally recognized forms of currency and have the ISO code XPT. However, there are only a few varieties of platinum coins minted, largely because of the cost of platinum and of the difficulty in working with it.

Bullion coins minted from platinum include the Manx Noble (minted from 1983 to 1989), the Canadian Platinum Maple Leaf (1988 to 1999), the Australian Platinum Koala (1988 to the present), the Mexican Libertad (1989 only), and the American Platinum Eagle (1997 to the present). The Chinese Platinum Panda were minted in three periods: from 1988 to 1990, 1993 to 1997, and lastly from 2002 to 2005.

Platinum accounts are offered by most banks in Switzerland. Here, platinum is treated like any other foreign currency; that is, it can be bought or sold instantly. However, bank clients are not entitled to ownership of the physical metal. Instead, they have a claim against their banks for a specified quantity of the metal.

The Least Dense Of The Platinum Group of Precious Metals Is Palladium

Palladium is a rare precious metal characterized by its lustrous silvery-white appearance. It was discovered by the English chemist William Hyde Wollaston in London, England in 1803, along with his discovery (together with Smithson Tennant, another English chemist) of the other metals in the platinum group. The name "palladium" was coined by Wollaston from the asteroid named "Pallas".

Of the different precious metals in the platinum group (which includes iridium, platinum, osmium, rhodium, and ruthenium), palladium is known to be the least dense. It likewise has the lowest melting point.

Palladium is utilized in many applications because of its unique properties, some of which are provided below.

General:

• Chemical Symbol: Pd

• Atomic Number: 46

• Category (as an element): Transition Metal

• Group/ Period/ Block (in the Periodic Table): 10/ 5/ d

• Atomic Weight: 106.42 g.mol-1

• Electron Configuration: [Kr] 4d10

Physical:

• Density (near room temperature): 12.023 g.cm-3

• Liquid Density (at melting point): 10.38 g.cm-3

• Melting Point: 1554.9°C, 2830.82°F, 1828.05°K

• Boiling Point: 2963°C, 5365°F, 3236°K

• Heat of Fusion: 16.74 kJ.mol-1

• Heat of Vaporization: 362 kJ.mol-1

Atomic:

• Oxidation States: 0, +1, +2, +4, +6

• Electronegativity: 2.2 (Pauling scale)

• Atomic Radius: 137 picometre

• Covalent Radius: 139±6 picometre

• Van der Waals Radius: 163 picometre

• Ionization Energies: 804.4 kJ.mol-1 (first), 1870 kJ.mol-1 (second), 3177 kJ.mol-1 (third)

Palladium is used in the following:

1. Catalytic converters;

2. Jewelry and watch making;

3. Dentistry and surgical instruments;

4. Aircraft spark plugs;

5. Electrical contacts;

6. Connector platings;

7. Manuscript illumination.

Since the late 1930s, palladium has been utilized as a precious metal in jewelry. Because of its naturally white properties, palladium has been used as an alternative to white gold. Along with silver and nickel, palladium is popularly used in making white gold alloys.

According to the British Geological Survey (BGS), the top four palladium-producing countries in the world are Russia, South Africa, Canada, and the United States (in this order). Russia produces at least half of the total amount of palladium produced in the world.

Commercially, palladium is produced from copper-nickel deposits in Siberia, South Africa, and in Ontario in Canada. The precious metal is also found - alloyed with the other metals in the platinum group as well as with gold - in Ethiopia, Australia, North and South America, and in the Ural Mountains in Russia.

The Norilsk Nickel Mining and Metallurgical Company in northern Russia is the largest single producer of palladium in the world. Significant amounts of mineable palladium are also found in two other places: the Lac des Îles igneous complex in northwestern Ontario, Canada and the Stillwater igneous complex in the state of Montana in the United States.

Such is the rarity and preciousness of palladium that many metric tons of ore have to be processed to obtain just a troy ounce of the precious metal. The ISO currency codes of palladium, as a commodity, are XPD and 964. Its price is approximately 150 U.S. dollars per troy ounce.

The Densest Precious Metal is Osmium

Osmium is an extremely hard, brittle, bluish white or gray transition metal in the platinum group metals. It is the densest natural element, being about 0.03 g/cm3 denser than iridium (the second densest natural element) and about twice as dense as lead. Among the platinum family members, osmium has the highest melting point and the lowest vapor pressure.

This precious metal is nearly impossible to fabricate. When alloyed with some of the other metals in the platinum group, such as iridium or platinum, osmium is used in certain applications where extreme hardness and durability are required. A couple examples of these are for electrical contacts and for tips of high quality fountain pens.

Some of the properties osmium possesses are outlined below.

General:

• Chemical Symbol: Os

• Atomic Number: 76

• Category (as an element): Transition Metal

• Group/ Period/ Block (in the Periodic Table): 8/ 6/ d

• Atomic Weight: 190.23 g.mol-1

• Electron Configuration: [Xe] 4f14 5d6 6s2

Physical:

• Density (near room temperature): 22.59 g.cm-3

• Liquid Density (at melting point): 20 g.cm-3

• Melting Point: 3033°C, 5491°F, 3306°K

• Boiling Point: 5012°C, 9054°F, 5285°K

• Heat of Fusion: 57.85 kJ.mol-1

• Heat of Vaporization: 738 kJ.mol-1

Atomic:

• Oxidation States: 8, 7, 6, 5, 4, 3, 2, 1, 0, -1, -2

• Electronegativity: 2.2 (Pauling scale)

• Atomic Radius: 135 picometre

• Covalent Radius: 144±4 picometre

• Ionization Energies: 840 kJ.mol-1 (first), 1600 kJ.mol-1 (second)

The name "osmium" was derived from the Greek word "osme", which means "smell". It was discovered by the English chemists William Hyde Wollaston and Smithson Tennant in London, England in 1803. Wollaston's and Tennant's discovery of the element involved the discovery as well of the other elements in the platinum group.

With an average mass fraction of 0.05 parts-per notation in the continental crust, osmium is known to be one of the least abundant elements in the Earth's crust. It is found in nature in natural alloys or as a pure element. Similar to the other precious metals in the platinum group, osmium can be found in alloys with copper or nickel.

The extreme toxicity and volatility of osmium's oxide makes it nearly impossible for this element to be used in its pure state. For this reason, it is often necessary to alloy osmium with other elements for use in high-wear applications. For example, osmiridium (a natural alloy of osmium and iridium) is alloyed with the other metals in the platinum group and used in instrument pivots and phonograph needles (apart from electrical contacts and fountain pen tips as mentioned earlier). In another example, osmium tetroxide is used to detect fingerprints and to stain fatty tissue for optical and electron microscopy.

Osmium occurs in the platinum-bearing river sands in North America, South America, and in the Ural Mountains in Russia. The latter, in fact, is known to be the site of the second largest alluvial deposit, which today is still mined. The approximate price of commercial osmium (99 percent pure osmium powder) is 100 U.S. dollars per gram.

Welcome Stranger And Hand Of Faith are the Largest Gold Nuggets of Precious Metals Discovered!

Gold nuggets are naturally occurring large masses of native gold found in alluvial deposits. Often they are concentrated by watercourses and recovered by placer mining. In other instances, gold nuggets are found in piles of residue in sites where mining operations once took place.

Two gold nuggets are noted for being the largest masses of gold ever discovered. These are the "Welcome Stranger" and the "Hand of Faith". Their respective "largest" titles, however, carry further qualifications.

The Welcome Stranger Gold Nugget:

The exact distinction given of this gold nugget is: "the largest alluvial gold nugget ever found". It was discovered on February 5, 1869 at Moliagul, a small township in Victoria, Australia about 37 miles west of the city of Bendigo. The discoverers, John Deason and Richard Oates, found the nugget just a couple inches below the surface on a slope in a place that's sometimes called Black Reef.

Records have the following details about the Welcome Stranger:

• Gross weight: 3,523.5 troy ounces (241.61 pounds)

• Trimmed weight: 2,520 troy ounces (172.8 pounds)

• Net weight: 2,315.5 troy ounces (158.78 pounds)

• Measurement: 2 feet (0.61 meter) x 1.02 feet (0.31 meter)

For their find, Deason and Oates were paid about £19,068 by the London Chartered Bank (located in the town of Dunolly in Victoria), where they took the nugget.

The Welcome Stranger no longer exists today, although the gold from it understandably still does. Also, there exist two replicas of the nugget. One is in possession of the descendants of John Deason, while the other is in the City Museum in Treasury Place, in Melbourne.

The Hand of Faith Gold Nugget:

This gold nugget actually carries two distinctions: "the largest gold nugget found by a metal detector" and "the largest gold nugget currently in existence". It was discovered on September 26, 1980 somewhere near the small town of Kingower in Victoria, Australia.

The nugget's discoverer, Kevin Hillier, was aided by a metal detector in this precious find. Hillier found the nugget in a vertical position just a foot below the surface.

The Hand of Faith weighs 874.82 troy ounces (60 pounds) and measures 1.54 feet (0.47 meter) x 0.66 feet (0.20 meter) x 0.30 feet (0.09 meter). The Golden Nugget Casino in Las Vegas, Nevada currently houses the nugget. Its sale price was reportedly around 1 million U.S. dollars.

Gold nuggets actually are not composed of pure 24K gold. A safer estimate would be that they're somewhere between 20K and 23K. Those found in Australia often have higher purity than the ones found in Alaska. The color of a nugget often provides a clue as to the purity of its gold content. Nuggets that have very rich deep orange/yellow color are sure to have higher gold content than pale ones.

Also, there is a system called "millesimal fineness" which is used to denote the purity of gold alloy (also of silver and platinum alloys) by parts per thousand of pure metal by mass in the alloy. A nugget containing 91.6% gold, for example, is denoted as "916 fine". This fineness is equivalent to 22K.

Is the Krugerrand The Most Well-Known Precious Metal Coin?

There are thirty-three known bullion coins in the world. Of these, 5 are made of platinum, 1 of palladium, 9 of silver, and 18 of gold. And of all these precious metal coins, the South African gold bullion coin Krugerrand is perhaps the most popular.

In 1967, the South African Mint Company introduced the Krugerrand, with the intention of circulating it as currency. Its status as a legal tender was seen as the best way for marketing South African gold around the world. In fact, thirteen years after its introduction, this precious metal coin accounted for about ninety percent of the gold coin market.

The Krugerrand comes in four varieties:

1. One-tenth ounce coin (0.11 troy ounce in weight, 1.35 millimeters thick, and 16.55 millimeters in diameter).

2. Quarter ounce coin (0.27 troy ounce in weight, 1.89 millimeters thick, and 22.06 millimeters in diameter).

3. Half ounce coin (0.55 troy ounce in weight, 2.22 millimeters thick, and 27.07 millimeters in diameter).

4. One ounce coin (1.09 troy ounces in weight, 2.84 millimeters thick, and 32.77 millimeters in diameter).

Each of these four coin varieties is 22K, containing 91.67% pure gold and 8.33% copper. This composition was meant to make the coins more durable and harder and thus resist dents and scratches, as, again, they were originally intended for circulation.

On the obverse of the Krugerrand is the face of Stephanus Jonannes Paulus Kruger, fifth president of the South African Republic (note the surname Kruger and the South African currency Rand were combined to give this precious metal coin its name). Also here are the Afrikaans and English versions of the name "South Africa", both inscribed in capital letters.

On the reverse of the coin is an image of the springbok, an antelope specie which is a South African national symbol. Atop the image is an inscription of the name of the coin, in capital letters, while below it is the coin's gold content, inscribed in Afrikaans and English.

Special samples of the coin (proof Krugerrand) are minted and offered as collector's items. These proof Krugerrands are priced above the bullion Krugerrands. The two coin versions can be distinguished from one another by the number of serrations they have - the proof version has 220, while the bullion has 40 less than the former's.

Other nations, such as Canada, Australia, the United States, and the United Kingdom, started producing their own precious metal coins one after the other beginning in 1979. The decisions of these gold-producing countries to mint their own bullion coins were most likely inspired by the success of the Krugerrand in its role as a vehicle for promoting the South African gold to the international market. As of 2008, about 1.3 million kilograms of South African gold, contained in Krugerrand coins, have been sold.

Unlike the bullion coin series of other countries, which come in gold and silver, the Krugerrand comes only in gold. Coins made of silver that are passed off as "Krugerrands" are neither produced by the South African Mint Company nor sanctioned by the government of South Africa.

The Most Corrosive Resistant Precious Metal is Iridium

Iridium is a transition metal belonging to the platinum group. Its main characteristics are that of being hard and brittle and of being silvery-white in appearance. It ranks next to osmium in being the densest element. As to its main property, this is best expressed in its being considered the most corrosive resistant of all the precious metals. In fact, this is shown even in temperatures of as high as 2000°C (3632°F or 2273.15°K).

Iridium was discovered in 1803 by the English chemist Smithson Tennant. It was identified from the residue of platinum ore which was dissolved in nitro-hydrochloric acid (also known as aqua regia). Platinum ores are still the main sources today of iridium. The precious metal is likewise obtained as a by-product of mining nickel.

Below are some of the properties of iridium.

General:

• Chemical Symbol: Ir

• Atomic Number: 77

• Category (as an element): Transition Metal

• Group/ Period/ Block (in the Periodic Table): 9/ 6/ d

• Atomic Weight: 192.217 g.mol-1

• Electron Configuration: [Xe] 4f14 5d7 6s2

Physical:

• Density (near room temperature): 22.56 g.cm-3

• Liquid Density (at melting point): 19 g.cm-3

• Melting Point: 2466°C, 4471°F, 2739°K

• Boiling Point: 4428°C, 8002°F, 4701°K

• Heat of Fusion: 41.12 kJ.mol-1

• Heat of Vaporization: 563 kJ.mol-1

Atomic:

• Oxidation States: -3, -1, 0, 1, 2, 3, 4, 5, 6

• Electronegativity: 2.20 (Pauling scale)

• Atomic Radius: 136 picometre

• Covalent Radius: 141±6 picometre

Because of its characteristic of being very brittle, pure iridium is quite difficult - almost impossible, in fact - to machine. Its primary use is as a hardening agent for platinum. High-temperature equipment, such as crucibles, are made from platinum-iridium alloys. Compass bearings, balances and fountain pen tips, on the other hand, are made from osmium-iridium alloys.

Again, iridium is the most corrosive resistant precious metal known. Coupled with its resistance to extremely high temperatures, this special characteristic makes iridium ideal for use in certain parts of aircraft engines. It is also alloyed with titanium to make deep-water pipes.

Other uses of iridium include the following:

1. Electrical contacts for spark plugs (due to its resistance to arc erosion);

2. Computer memory devices;

3. Direct-ignition engine (as a catalyst);

4. Radiotherapy (as a source of radiation);

5. X-ray telescopes.

In 2007, worldwide demand for iridium reached 3,701 kilograms (119,000 troy ounces). Distribution of these were as follows: electrochemical uses (1,100 kilograms); electrical uses (780 kilograms); for catalysis (750 kilograms); and other applications (1,100 kilograms).

Iridium is found at highest concentrations within the Earth's crust in three specific types of geologic structures: in impact craters, in igneous deposits, and in deposits reworked from either of the first two. The Bushveld igneous complex in South Africa is the largest known primary reserves for iridium in the world. Other important sources of this precious metal are the Sudbury Basin in Canada and the nickel-copper-palladium deposits near Norilsk in Russia. Several smaller iridium reserves are also found in the United States.

Beginning the year 2000, the annual production of iridium is about 3 tonnes (96,500 troy ounces). Its price as of 2007 is 14,667 U.S. dollars per kilogram (440 U.S. dollars per troy ounce).

Definition And The Three Distinct Kinds of Gold Standard of Precious Metals

The gold standard is defined in many different reference materials as a monetary system in which the unit of currency used is a fixed quantity or weight of gold. Under this system, all forms of money, including notes and bank deposits, were freely converted into gold at the fixed price.

There are three known kinds of gold standard that have been adopted since the early 1700s - the gold specie, gold exchange, and gold bullion standards. Following is the definition and a brief historical account of each.

Gold Specie Standard:

In this gold standard, the unit of currency is linked to the gold coins that are in circulation. More specifically, the monetary unit is associated with the unit of value of a specific gold coin in circulation along with that of any secondary coinage (coins made of metal that is valued less than gold).

Recorded history points to the existence of a gold specie standard in medieval empires. For example, the Eastern Roman Empire made use of a gold coin called Byzant (from the original Greek term Bezant). The first known major area in the world to be on a gold specie standard in modern times is the British West Indies. That standard, however, was more of a commonly applied system rather than an officially established one. It was based on the Spanish gold coin called the doubloon.

The United States adopted the gold specie standard "de jure" (by law) in 1873, using the American Gold Eagle as unit.

Gold Exchange Standard:

In this gold standard, only the circulation of coins minted from lesser valuable metals (such as silver) may be involved. The authorities, however, will have undertaken a fixed exchange rate with a country that's on the gold standard.

Before the turn of the 20th century, countries that were still on silver standard started pegging their monetary units to the gold standard of either the United States or the United Kingdom. For example, Mexico, the Philippines, and Japan pegged their respective silver units to the U.S. dollar at fifty cents.

Gold Bullion Standard:

In this gold standard, gold bullion is sold on demand at a fixed price. It was introduced in 1925 by the British Parliament in an act which at the same time voided the gold specie standard. Six years later, the United Kingdom decided to temporarily stop the gold bullion standard because of the large amount of gold that flowed out across the Atlantic Ocean. The gold standard eventually ended that same year.

One of the advantages of the gold standard is that it sort of restricts the government's power in inflating prices, which is possible through excessive issuance of paper currency. Also by providing a fixed pattern of exchange rates, the gold standard may effectively lessen uncertainty in international trade.

As to its disadvantage, the gold standard may make monetary policy ineffective in stabilizing the economy in the event of a general slowdown in economic activity. This is likely, as many economists fear, since under the gold standard the supply of gold would be the exclusive determinant to the amount of money.

Using Gold As An Investment for Precious Metals

Four of the nine known precious metals are regarded as investment commodities. Of these four, gold is the most popular. Investing in gold is a way of protecting against crises that may be brought about by economic or political instability or by social unrest.

There are at least six ways of investing in gold:

Buying gold coins:

This is the most popular way of investing in gold. Gold bullion coins are typically priced based on their weight; a premium is added to the gold spot price. Gold coins may be bought or sold over the counter in most Swiss banks.

Buying gold bars:

This is the most traditional way of investing in gold. As in gold bullion coins, bullion gold bars can be bought or sold over the counter in most Swiss banks, as well as in major banks in Liechtenstein and Austria. There also are bullion dealers that provide this same kind of service. Gold bars however are becoming less and less an option among investors due to the difficulties (in the verification process, transportation, and storage) associated with them.

Opening a gold account:

Gold accounts are offered by most banks in Switzerland. Here, gold can be bought or sold in much the same way foreign currencies are dealt. A gold account is backed either through non-fungible (allocated) gold storage or pooled (unallocated) storage.

Owning a gold certificate:

A gold investor may opt to hold on to a gold certificate rather than store the physical gold bullion. The gold certificate allows the investor to buy and sell the security and do away with the many difficulties associated with the actual gold's transfer.

Trading in Gold Exchange-Traded Funds (GETFs):

Trading in GETFs is like trading shares in, say, the New York Stock Exchange or the London Stock Exchange. Gold Bullion Securities, the first GETF introduced (in 2003, on the Australian Stock Exchange), stood for 1/10 of an ounce of gold. GETFs are a good means of gaining exposure to the price of gold, minus the inconvenience of storage. Trading in GETFs involves payment of commission and storage fee (charged on an annual basis). The expenses incurred in relation to the handling of the fund are charged through the selling of a certain amount of the gold as represented by the certificate. Over time, the amount of gold in the certificate, as may be expected, decreases.

Entering in a Contract For Difference (CFD):

Some of the noted financial services firms, especially those in the United Kingdom, provide Contract for Difference (CFD). In this gold investment vehicle, two parties (a "buyer" and a "seller") enter into a contract, in which the seller agrees to pay the buyer the difference between the current value of gold and its value at contract time. In case the difference is negative, the seller receives payment instead from the buyer. A CFD, therefore, allows an investor to take advantage of long or short positions, enabling him/her to speculate on these markets.

In a related scenario, an investor may buy gold early in a condition where there is increased investor confidence. The investor then sells the gold before a general decline in the stock market sets in. Obviously in this case, the investor's aim is to gain financially.

Is Gold The Most Sought After Precious Metal?

Of all the different precious metals we can think of, gold is certainly the one most greatly desired. Since the beginning of recorded history, gold has been in use in many different works of art, coinage, and, of course, jewelry. Occurring as grains in rocks and in alluvial deposits, gold is shiny, soft, and dense. It is known to be the most ductile and malleable pure metal.

What makes pure gold especially attractive is its bright yellow color and luster. These characteristics are maintained as gold is chemically unaffected by air or moisture. Here are some of the properties of gold:

General:

• Chemical Symbol: Au

• Atomic Number: 79

• Category (as an element): Transition Metal

• Group/ Period/ Block (in the Periodic Table): 11/ 6/ d

• Atomic Weight: 196.966569(4) g.mol-1

• Electron Configuration: [Xe] 4f14  5d10 6s1


Physical:

• Density (near room temperature): 19.30 g.cm-3

• Liquid Density (at melting point): 17.31 g.cm-3

• Melting Point: 1064.18°C, 1947.52°F, 1337.33°K

• Boiling Point: 2856°C, 5173°F, 3129°K

• Heat of Fusion: 12.55 kJ.mol-1

• Heat of Vaporization: 324 kJ.mol-1


Atomic:

• Oxidation States: -1, 1, 2, 3, 4, 5

• Electronegativity: 2.54 (Pauling scale)

• Atomic Radius: 144 picometre

• Covalent Radius: 136±6 picometre

• Van der Waals Radius: 166 picometre

• Ionization Energies: 890.1 kJ.mol-1 (first), 1980 kJ.mol-1 (second)

The term "gold" was derived from "geolu", an Old English Anglo-Saxon word which means "yellow". Its symbol "Au", on the other hand, originated from "aurum", the Latin word for "gold". The exact period when gold was first discovered could be a subject of dispute. While some accounts point to the year 1848 when gold was discovered in California, history tells us that this precious metal was already being used extensively by the ancient Egyptians, Romans, Greeks, Chinese, and South Americans. 

Throughout history, gold has served as a measure of value and a symbol of wealth. It is one of the coinage metals (along with silver and copper). It is used, customarily and legally, as a means of payment or a medium of exchange. Gram and troy weight are the units of measurement used for gold. To indicate the amount of gold present in, say, a piece of jewelry, the term "carat" is used. A necklace, for instance, that is 24 carats means that it is made of pure gold.

While gold's price is determined through trading in the derivatives and gold markets, its daily benchmark price is provided in a procedure called the London Gold Fix. In this procedure, the price of the precious metal is determined each business day on the London market. The fixing is done twice - once in the morning and another in the afternoon. The latter actually was introduced about 49 years after the procedure itself was introduced, as a means of providing a price when US markets are open.

This gold-price fixing procedure is done by the five members of the London Gold Market Fixing Ltd., namely The Bank of Nova Scotia, Barclays Capital, Deutsche Bank AG London, HSBC, and Societe Generale Corporate & Investment Banking.

Silver and Gold Traditional Coinage Precious Metals

Four transition metals make up group 11 of the periodic table of elements. All, except one, are considered traditional coinage metals. Qualifying this further, only two of these three traditional coinage metals are considered precious metals. These are gold and silver.

Gold and silver are rare and have high economic values. These things can't be said of copper, the other traditional coinage metal. Occurring in nature in metallic form, these two precious metals can be produced sans the use of extraction metallurgy. These other characteristics of gold and silver make them both well suited for coinage:

• They are not radioactive.

• They are more ductile or softer than most other elements.

• They are less reactive compared with other elements.

• They have excellent luster.

• They have higher melting points compared with other metals.

The high-ductility property of gold and silver means they can be easily damaged as coins for circulation. Coins intended for circulation must be highly resistant to corrosion and wear. For this reason, gold or silver must be alloyed with other metals (example, manganese) so that the resulting coins will come out harder, more wear-resistant, and not easily damaged or deformed.

As numismatic items, gold and silver coins are made almost entirely of the precious metals, respectively. Current collectible gold coins (the 22-carat gold coins), for example, are made of 92% gold, with silver and copper comprising the rest. The coins in circulation in the United States prior to 1933 were made of 90% gold and 10% copper-silver combined. Canada's official gold bullion coin - The Canadian Gold Maple Leaf - is made of 99.999% gold; and so are these four other gold bullion coins:

1. British Britannia (with a face value of 100 pounds).

2. Chinese Gold Panda (with face values of 500, 200, 100, 50, and 25 Yuan).

3. Swiss Helvetia Head (with face values of 100, 20, and 10 Swiss francs).

4. Austrian Vienna Philharmonic (with face values of 100, 50, 25, and 10 euros).

Silver coins, like the minted coins circulated in the United States and other countries prior to 1965, were made of 90% silver and 10% copper. The American Silver Eagle and the Mexican Silver Libertad bullion coins, introduced in 1986 and 1982 respectively, were made of 99.9% silver and 0.1% copper.

Other notable silver bullion coins include the Australian Silver Kookaburra, Chinese Silver Panda, and the Russian George the Victorious.

Minting coins, whether gold or silver, always entails the risk of having the value of the metal used in the coin greater than the coin's face value. This is especially true in coins of low denomination. Because of this, there exists the possibility of some smelters taking gold or silver coins and melting these down for the scrap value of the precious metals.

A couple examples, in this regard, are worth mentioning here: US pennies have been made of copper-clad zinc since 1982, when they were before this time made of copper alloys; and British pennies were once made of 97% copper, but are now made of copper-plated steel.

As additional information, gold and silver both have a currency code of ISO 4217.

Bullion: Mass Of Precious Metals

Bullion is a mass of any one of the known precious metals. By strict definition, precious metals are those metallic elements that are rare. Bullion is commonly made of either gold or silver. Its value is determined by the worth of the metal rather than by its face value as money. To put it another way, bullion is valued based on the mass and purity of the metal used, instead of its artificial currency value.

New sources of ore have been discovered and there also have been improvements in the mining and refining processes. These two factors may cause the values of gold, silver, and the other precious metals to diminish. Also, the "precious" qualification of a metal is determined by the market value or high demand.

Bullion is traded on commodity markets in two forms: bulk ingots or coins, the latter minted by the government of a country. At least ten countries are known to mint gold and silver bullion coins. These are Australia, Austria, Canada, China, Mexico, Poland, South Africa, Switzerland, the United Kingdom, and the United States.

While bullion coins are issued as legal tender, with nominal values assigned to them on minting, such face values are far below the commodity value of the metals themselves. Here's an example: Most of the gold coins issued by national governments, particularly those with currency values of between 10 and 100 U.S. dollars, usually contain no less than 31 grams of gold. On the average (considering the consistent rise in the exchange rate of gold), the value of gold is around USD12 per gram. Here, it is clear that the currency value assigned by the government to a gold bullion coin has no meaning.

Below is a list of some of the government-issued gold and silver bullion coins:

1. Australian Gold Nugget, Lunar Series I, and Lunar Series II

2. Austrian Philharmoniker

3. Canadian Maple Leaf

4. Chinese Gold Panda

5. Mexican Centenario, Libertad, and Onza

6. Polish Orzel bielik

7. South African Krugerrand

8. Swiss Vreneli

9. British Britannia and Sovereign

10. American Buffalo, American Eagle, and Double Eagle

The 10,000-dollar Australian Gold Nugget is one of the world's largest bullion coins. Minted by the Australian government, this bullion coin is made of 1 kilogram of 99.9% pure gold. Some other bullion coins larger than the Australian Gold Nugget have come out. However, these are not produced in mass quantities and are not practical to handle. Two examples are given here: One is the 100,000-euro Vienna Philharmonic, minted in 2004, which contains 31 kilograms of gold; the other is the 1 million-dollar Canadian Maple Leaf, minted in 2007, which contains 100 kilograms of gold.

Three factors - metal, purity, and weight - affect the value of bullion. The overall value of bullion is determined by the metal used. We know, of course, that platinum is worth more than gold, which, in turn, is worth more than silver. It is easy to understand, therefore, that silver bullion coins have become popular with collectors because of their relative affordability.