“Precious” metals are gold, silver or any of what are now called the PGM or “platinum group metals” (platinum, iridium, palladium, ruthenium, rhodium and osmium); all others are “base” or ”industrial” metals. “Precious” refers only to their use in jewelry; many “base” metals are extremely valuable to industry. For example, copper is a monetary metal, used in coinage for millennia, and rhenium’s value is nearly ten times that of gold, but it’s so rare the entire output is committed to industrial use. Likewise, precious metals have industrial applications. Only two-thirds of gold mined and less that forty percent of silver becomes jewelry or coins. The rest goes to electronics, photography, medicine or elsewhere.
Purity is always an important question when buying precious metal. Purity is generally described in “fineness” or parts per thousand. The standard is 999 fine or 99.9 percent pure.
Part of the precious metal mystique is tradition — silver and gold have been valued as decoration and currency since ancient times. They are rare, but common enough to form a worldwide standard. They are easy to work and they don’t rust. The platinum group joined the precious category because their properties are similar to gold and silver, and they are also very pretty to look upon. Recently, some industrial metals have found their way into bracelets, earrings, necklaces and rings because these elements have advantages over precious metals.