| In chemistry, the term base metal is used | | | | commodities. Gold, silver, platinum and |
| informally to refer to a metal that oxidizes | | | | palladium each have an ISO 4217 currency |
| or corrodes relatively easily, and react | | | | code. |
| variably with dilute hydrochloric acid (HCl) | | | | |
| to form hydrogen. Examples include iron, | | | | The best-known precious metals are gold and |
| nickel, lead and zinc. Copper is considered a | | | | silver. While both have industrial uses, they |
| base metal as it oxidizes relatively easily, | | | | are better known for their uses in art, |
| although it does not react with HCl. It is | | | | jewelry, and coinage. Other precious metals |
| commonly used in opposition to noble metal. | | | | include the Platinum group metals: ruthenium, |
| | | | rhodium, palladium, osmium, iridium, and |
| In alchemy, a base metal was a common and | | | | platinum, of which platinum is the most |
| inexpensive metal, as opposed to precious | | | | widely traded. |
| metals, mainly gold and silver. A longtime | | | | |
| goal of the alchemists was the transmutation | | | | The demand for precious metals is driven not |
| of base metals into precious metals. | | | | only by their practical use, but also by |
| | | | their role as investments and a store of |
| In numismatics, coins used to derive their | | | | value. Palladium is, as of February 20 2007, |
| value primarily from the precious metal | | | | valued at ($337.50 USD per ounce) slightly |
| content. Most modern currencies are fiat | | | | above half the price of gold ($658.58 USD |
| currency, allowing the coins to be made of | | | | ounce), and platinum ($1210.50 USD/ounce) at |
| base metal. | | | | around twice that of gold. Silver is |
| | | | substantially less expensive ($13.84 USD |
| One method of classifying metals is by their | | | | ounce) than these metals, presently at about |
| content, and one common division is into | | | | 1/50 the price of gold, but is often |
| ferrous metals and non-ferrous metals. The | | | | traditionally considered a precious metal for |
| term ferrous is derived from the Latin | | | | its role in coinage and jewellery. Rhodium |
| "Ferrum" which means "containing iron", thus | | | | though is the most expensive of the precious |
| ferrous metals contain iron and non ferrous | | | | metals with prices as high as $6200.00 USD |
| metals do not. Ferrous metals may be pure | | | | per ounce (as of December 29, 2006). |
| iron, like wrought iron, or they may be | | | | |
| alloys of iron and other elements. Steel, | | | | Bullion |
| being an alloy of iron and carbon, would | | | | |
| therefore be a ferrous metal. | | | | Precious metals in bulk form are known as |
| | | | bullion, and are traded on commodity markets. |
| Ferrous metals are often magnetic, but this | | | | Bullion metals may be cast into ingots, or |
| property is not in and of itself sufficient | | | | minted into coins. The defining attribute of |
| to classify a metal as ferrous or | | | | bullion is that it is valued by its mass and |
| non-ferrous. Austenitic stainless steel, a | | | | purity rather than by a face value as money. |
| ferrous metal, is non-magnetic, while cobalt | | | | Many nations mint bullion coins, of which the |
| is magnetic but non-ferrous. However since | | | | most famous is probably the gold South |
| ferrous metals are the most common magnetic | | | | African Krugerrand. Although nominally issued |
| materials, magnets are commonly used to | | | | as legal tender, these coins' face value as |
| separate them from non-ferrous metals and | | | | currency is far below that of their value as |
| other materials. | | | | bullion. For instance, the United States |
| | | | mints a gold bullion coin (the Gold Eagle) at |
| Common ferrous metals include the various | | | | a face value of $50 containing 1 troy ounce |
| irons and steels. Common non-ferrous metals | | | | (31.1035 g) of gold — as of January |
| include aluminium, tin, copper, zinc, and | | | | 2006, this coin is worth about $550 as |
| brass, an alloy of copper and zinc. The | | | | bullion. Bullion coins' minting by national |
| precious metals silver, gold, and platinum | | | | governments gives them some numismatic value |
| are also non-ferrous. | | | | in addition to their bullion value, as well |
| | | | as certifying their purity. The level of |
| Noble metals are metals that are resistant to | | | | purity varies from country to country, with |
| corrosion or oxidation, unlike most base | | | | some bullion coins of as pure as 99.99% |
| metals. They tend to be precious metals, | | | | available, such as the Canadian Gold Maple |
| often due to perceived rarity. Examples | | | | Leaf. Note that a 100% pure bullion is not |
| include gold, silver, tantalum, platinum, and | | | | possible, as absolute purity in extracted and |
| rhodium. | | | | refined metals can only be asymptotically |
| | | | approached. |
| Some of the noble metals can be dissolved in | | | | |
| aqua regia, a highly concentrated mixture of | | | | One of the largest bullion coins in the world |
| acids. | | | | is the 10,000 dollar Australian Gold Nugget |
| | | | coin minted in Australia which consists of a |
| Alchemists were concerned with the | | | | full kilogram of 99.9% pure gold; however |
| transmutation of base metals into gold (a | | | | China has produced coins in very limited |
| noble metal) for economic gain, or as a | | | | quantities (less than 20 pieces minted) that |
| metaphor for more esoteric processes. | | | | exceed 260 troy ounces (8 kg) of gold. |
| | | | |
| The term can also be used in a relative | | | | Gold as an investment and silver as an |
| sense. A "Galvanic series" is a hierarchy of | | | | investment are often seen as a hedge against |
| metals (or other electrically conductive | | | | both inflation and economic downturn. Silver |
| materials, including composites and | | | | coins have become popular with collectors due |
| semimetals) that runs from noble to active, | | | | to their relative affordability, and unlike |
| and allows designers to see at a glance how | | | | most gold and platinum issues which are |
| materials will interact in the environment | | | | valued based upon the markets, silver issues |
| used to generate the series. In this sense of | | | | are more often valued as collectables, far |
| the word, graphite is more noble than silver | | | | higher than their actual bullion value. |
| (even though it is alchemically more base) | | | | |
| and the relative nobility of many materials | | | | Precious metal status |
| is highly dependent upon context, as for | | | | |
| aluminium and stainless steel in conditions | | | | A metal is deemed to be precious if it is |
| of varying pH. | | | | rare. The discovery of new sources of ore or |
| | | | improvements in mining or refining processes |
| In physics the definition of a noble metal is | | | | may cause the value of a precious metal to |
| even more strict. It is required that the | | | | diminish. The status of a "precious" metal |
| d-bands of the electronic structure are | | | | can also be determined by high demand or |
| filled. Taking this into account, only | | | | market value. |
| copper, silver and gold are noble metals, as | | | | |
| all d-like band are filled and don't cross | | | | An interesting case of a once-precious metal |
| the Fermi level. For platinum two d-bands | | | | that is now common is that of aluminium. |
| cross the Fermi level, changing its chemical | | | | Although aluminium is one of the most |
| behaviour; it is used (in contrast to e.g. | | | | commonly occurring elements on Earth, it was |
| gold) as a catalyst. The different reactivity | | | | initially found to be exceedingly difficult |
| can easily be seen while preparing clean | | | | to extract from its various ores. This made |
| metal surfaces in ultra high vacuum; surfaces | | | | aluminium more valuable than gold. Bars of |
| of noble metals (e.g. gold) are easy to clean | | | | aluminium were exhibited alongside the French |
| and stay clean for a long time, while those | | | | crown jewels at the Exposition Universelle of |
| of e.g. platinum or palladium are covered by | | | | 1855, and Napoleon III was said to have |
| carbon monoxide very quickly. | | | | reserved a set of aluminium dinner plates for |
| | | | his most honored guests. Additionally, the |
| Precious metals in bulk form are known as | | | | pyramidal top to the Washington Monument is |
| bullion. A precious metal is a rare metallic | | | | made of pure aluminium, as at the time of the |
| chemical element of high economic value. | | | | monument's construction, aluminium was more |
| | | | expensive than silver, gold, or platinum. |
| Chemically, the precious metals are less | | | | Over time, however, the price of the metal |
| reactive than most elements, have high | | | | gradually dropped; the discovery of the |
| luster, and have higher melting points than | | | | Hall-Héroult process in 1886 caused the |
| other metals. Historically, precious metals | | | | high price of aluminium to permanently |
| were important as currency, but are now | | | | collapse. |
| regarded mainly as investment and industrial | | | | |