A metal is deemed to be
precious 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 high
demand or
market value. Precious metals in bulk form are known as
bullion and are traded on international bullion markets. Bullion metals may be cast into
ingots or minted into
coins. The defining attribute of bullion is that it is valued by its mass and purity rather than by a
face value as
money.
Purity and mass The level of purity varies from issue to issue. "Three nines" (99.9%) purity is common. The purest mass-produced bullion coins are in the
Canadian 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 of
alloy, with the purity a local standard. The
Krugerrand is the first modern example of measuring in "pure gold": it should contain at least
ounces of at least pure gold. Other bullion coins (for example the
British Sovereign) show neither the purity nor the fine-gold weight on the coin but are recognized and consistent in their composition. Many coins historically showed a
denomination in currency (example: American
double eagle: $20).
Coinage Many nations mint
bullion coins. Although nominally issued as
legal tender, these coins' face value as currency is far below their value as bullion. For instance, Canada mints a
gold bullion coin (the
Gold 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 to OANDA Historical Exchange Rates. Although the exact moment that the $1,075 figure was determined is unknown, it may be considered a reasonable value for the time. Bullion coins' minting by national governments gives them some
numismatic value in addition to their bullion value, as well as certifying their purity. bullion coin One of the largest bullion coins in the world was the 10,000-dollar
Australian 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. China has produced coins in very limited quantities (less than 20 pieces minted) that exceed of gold. Austria has minted a coin containing 31 kg of gold (the
Vienna 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 the
Royal 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. The
Reserve Bank of Zimbabwe mints the gold
Mosi-oa-Tunya (coin) which is recognized as
legal tender at the market value for its gold content.
Economic use Gold and
silver, and sometimes other precious metals, are often seen as defensive assets against both
inflation and economic downturn. The
gold-to-silver ratio, which measures how many ounces of silver are needed to purchase one ounce of gold, is one of the oldest continuously tracked price relationships and is widely used by investors to assess relative value between the two metals.
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 collectables, at far higher than their bullion value.
Industrial use Platinum and
palladium are key catalysts in
hydrogenation reactions and emission-reducing catalytic converters, while gold is used in oxidation reactions and nanotechnology due to its stability.
Platinum group metals (PGMs) have been used in the production of
sulfuric and
nitric acid for centuries. Additionally,
gold and
silver nanoparticles are used in
biosensors and solar cells, underscoring their value in sustainable technologies. ==Aluminium==