Precious metals are rare, naturally occurringmetallicchemical elements of higheconomic value. Precious metals, particularly thenoble metals, are morecorrosion resistant and lesschemically reactive than most elements. They are usuallyductile and have a highlustre. Historically, precious metals were important ascurrency but they are now regarded mainly as investment and industrialraw materials.Gold,silver,platinum, andpalladium each have anISO 4217 currency code.
The best known precious metals are the preciouscoinage metals, which are gold and silver. Although both have industrial uses, they are better known for their uses inart,jewelry, and coinage. Other precious metals include theplatinum group metals:ruthenium,rhodium,palladium,osmium,iridium, andplatinum, of which platinum is the most widely traded.[1]The demand for precious metals is driven not only by their practical use but also by their role asinvestments and astore of value. Historically, precious metals have commanded much higher prices than common industrial metals.
A metal is deemed to beprecious if it is rare. The discovery of new sources of ore or improvements in mining or refining processes may cause the value of a precious metal to diminish. The status of a "precious" metal can also be determined by highdemand ormarket value. Precious metals in bulk form are known asbullion and are traded on international bullion markets. Bullion metals may be cast intoingots or minted intocoins. The defining attribute of bullion is that it is valued by its mass and purity rather than by aface value asmoney.
The level of purity varies from issue to issue. "Three nines" (99.9%) purity is common. The purest mass-produced bullion coins are in theCanadian Gold Maple Leaf series, which go up to 99.999% purity. A 100% pure bullion is nearly impossible: as the percentage of impurities diminishes, it becomes progressively more difficult to purify the metal further. Historically, coins had a certain amount of weight ofalloy, with the purity a local standard. TheKrugerrand is the first modern example of measuring in "pure gold": it should contain at least12⁄11ounces of at least11⁄12 pure gold. Other bullion coins (for example theBritish Sovereign) show neither the purity nor the fine-gold weight on the coin but are recognized and consistent in their composition.[citation needed] Many coins historically showed adenomination in currency (example: Americandouble eagle: $20).
Many nations mintbullion coins. Although nominally issued aslegal tender, these coins' face value as currency is far below their value as bullion. For instance, Canada mints agold bullion coin (theGold Maple Leaf) at a face value of $50 containing one troy ounce (31.1035 g) of gold, as of January 2022. The USD to CAD exchange rate averaged 1.129 in July 2009 according toOANDA Historical Exchange Rates. Although the exact moment that the $1,075 figure[clarification needed] was determined is unknown, it may be considered a reasonable value for the time. Bullion coins' minting by national governments gives them somenumismatic value in addition to their bullion value, as well as certifying their purity.
One of the largest bullion coins in the world was the 10,000-dollarAustralian Gold Nugget coin minted in Australia, which consists of a full kilogram of 99.9% pure gold. In 2012, the Perth Mint produced a 1-tonne coin of 99.99% pure gold with a face value of$1 million AUD, making it the largest minted coin in the world with a gold value of around$50 million AUD.[2] China has produced coins in very limited quantities (less than 20 pieces minted) that exceed 8 kilograms (260 ozt) of gold.[citation needed] Austria has minted a coin containing 31 kg of gold (theVienna Philharmonic Coin minted in 2004 with a face value of 100,000 euro). As a stunt to publicise the 99.999% pure one-ounce Canadian Gold Maple Leaf series, in 2007 theRoyal Canadian Mint made a 100 kg 99.999% gold coin, with a face value of$1 million, and now manufactures them to order, but at a substantial premium over the market value of the gold.[3][4]
TheReserve Bank of Zimbabwe mints the goldMosi-oa-Tunya (coin) which is recognized aslegal tender at the market value for its gold content.[5]
Gold andsilver, and sometimes other precious metals, are often seen as defensive assets against bothinflation and economic downturn.Silver coins have become popular with collectors due to their relative affordability, and, unlike most gold and platinum issues which are valued based upon the markets, silver issues are more often valued as collectibles, at far higher than their bullion value.[6]
Platinum andpalladium are key catalysts inhydrogenation reactions and emission-reducing catalytic converters,[7] while gold is used in oxidation reactions and nanotechnology due to its stability.[8]Platinum group metals(PGMs) have been used in the production ofsulfuric andnitric acid for centuries.[9] Additionally,gold andsilver nanoparticles are used inbiosensors and solar cells, underscoring their value in sustainable technologies.[10]
Aluminium is now commonplace but was considered to be a precious metal until the late 1800s. Although aluminium is thethird most abundant element and themost abundant metal in the Earth's crust, it was at first found to be exceedingly difficult to extract the metal from its various non-metallicores. The great expense of refining the metal made the small available quantity of pure aluminium more valuable than gold.[11] Bars of aluminium were exhibited at theExposition Universelle of 1855,[12] andNapoleon III's most important guests were given aluminium cutlery, while those less worthy dined with mere silver.[11] In 1884, the pyramidal capstone of theWashington Monument was cast of 100 ounces of pure aluminium. By that time, aluminium was as expensive as silver.[13] The statue ofAnteros atop theShaftesbury Memorial Fountain (1885–1893) in London'sPiccadilly Circus is also of cast aluminium. Over time, however, the price of the metal has dropped. The dawn of commercial electric generation in 1882 and the invention of theHall–Héroult process in 1886 caused the price of aluminium to drop substantially over a short period of time.[14]
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| Metal | Mass abundance (ppb)[15] | Metal price (US$/kg) | ||||||
|---|---|---|---|---|---|---|---|---|
| Name | Symbol | 10 Apr 2009 [16] | 22 Jul 2009 [17] | 7 Jan 2010 [citation needed] | 31 Dec 2014 [18] | 16 Jul 2018 [19][unreliable source?] | 2 Mar 2023 [20] | |
| Ruthenium | Ru | 1 | 2,290 | 2,730 | 5,562 | 1,865 | 8,423[21] | 14,950 |
| Rhodium | Rh | 1 | 39,680 | 46,200 | 88,415 | 39,641 | 77,804[22] | 302,220 |
| Palladium | Pd | 15 | 8,430 | 8,140 | 13,632 | 25,559 | 32,205 | 46,440 |
| Silver | Ag | 75 | 437 | 439 | 588 | 441 | 556 | 670 |
| Indium | In | 50[23] | 520 | |||||
| Tellurium | Te | 1 | 158.70 | |||||
| Rhenium | Re | 0.7 | 7,400 | 7,000 | 6,250 | 2,425 | ||
| Osmium | Os | 1.5 | 13,400 | 12,200 | 12,217 | 12,217 | ||
| Iridium | Ir | 1 | 14,100 | 12,960 | 13,117 | 15,432 | 46,940[24] | 147,890 |
| Platinum | Pt | 5 | 42,681 | 37,650 | 87,741 | 38,902 | 28,960 | 31,010 |
| Gold | Au | 4 | 31,100 | 30,590 | 24,317 | 38,130 | 43,764 | 59,040 |
| Mercury | Hg | 85 | 18.90 | 15.95 | ||||
| Bismuth | Bi | 8.5 | 15.40 | 18.19 | ||||
