Only two of the three traditional coinage metals are considered precious metals. These are gold and silver.
Gold and silver are rare metals with high economic value. These qualities can't be attributed to copper, the other traditional coinage metal. Occurring in nature in metallic form, these two precious metals can be produced without the use of extraction metallurgy. Other characteristics of gold and silver make them both ideal for coinage:
• They are more ductile or soft than most other elements.
• They have excellent luster.
• They have higher melting points compared with other metals.
The high-ductility properties of gold and silver mean that they can be easily damaged as coins during circulation. Coins intended for circulation must be highly resistant to corrosion and wear. For this reason gold or silver must be alloyed with harder metals such as manganese so that the coins will come out harder and durable.
Gold and silver coins however, are made almost entirely of the precious metals. Current collectible gold coins such as the 22-carat gold coin, 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. Canada's official gold bullion coin, the Canadian Gold Maple Leaf, is made of 99.999% gold.
Here are four other popular gold bullion coins:
1. British Britannia (face value of 100 pounds).
2. Chinese Gold Panda (face values of 500, 200, 100, 50, and 25 Yuan).
3. Swiss Helvetia Head (face values of 100, 20, and 10 Swiss francs).
4. Austrian Vienna Philharmonic (face values of 100, 50, 25, and 10 euros).
Other notable silver bullion coins include the Australian Silver Kookaburra, Chinese Silver Panda, and the Russian George the Victorious.
Silver coins, like those minted 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 the 1980’s, were made of 99.9% silver and 0.1% copper.
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. Therefore, there’s always the risk of some smelters taking gold or silver coins and melting these down for the scrap value of the precious metals.
A couple examples are US pennies which have been made of copper-clad zinc since 1982, (before this they were made of copper alloys) and British pennies ( once made of 97% copper) are now made of copper-plated steel.
