Silver is one of the most versatile metals on the planet. It is highly conductive, which makes it usefully in electronics and in wiring. It also has antibacterial properties that are increasingly being applied to prevent food and water spoilage and to treat infection. But probably the most visible use of silver is as jewellery and flatware. The most common form of silver for these uses is sterling silver, which is defined as silver of 92.5 per cent purity or higher that is not fine silver.
Investment grade, or fine, silver is 99.9 per cent (.999) pure or better. The Silver Maples produced by the Royal Canadian Mint are 99.99 per cent (.9999) pure silver. But pure silver has some qualities that can be undesirable in particular applications. It is soft and bendable, and oxidises easily producing a tarnish. Jewellery makers and other users of silver often mix silver with other metal to make it more suitable for their purposes. Silver of between 92.5 per cent purity and fine is called sterling silver.
The standard content of sterling silver is 92.5 per cent (.925) silver and 7.5 per cent copper. The presence of the copper increases the hardness of the alloy, making it less likely to bend. It also slows down the rate of oxidation so silver jewellery and flatware doesn't tarnish as quickly as fine silver. Sterling silver is usually identified with a marking of "925" or "ster" on the bottom or rear of a sterling silver piece.
A different alloy of sterling silver, called argentium, is also created with 92.5 per cent silver. Argentium, however, replaces a small amount of the copper with a metal called germanium. This special alloy is useful in applications that have exposure to high temperature since it reduces the firescale that forms in normal sterling silver. It also has even higher tarnish resistance than ordinary sterling silver.
Silver of 95 per cent purity is relatively rare because it is a nonstandard alloy. Technically it is not fine silver because it falls considerably below 99.9 per cent fineness. This means it is sterling silver, but more pure than most sterling silver. 950 silver will be softer than most sterling silver and will tarnish more easily. This means it is unlikely to be used in most industrial applications. Most 950 silver is used for jewellery.
In 2007 a U.S. patent issued for an alloy of sterling silver with "enhanced tarnish resistance" and "exceptional" hardness. Like most sterling silver, this alloy contains 92.5 per cent silver. But it only has about 5.25 per cent copper. The remainder is made of zinc, tin, lithium, silicon, germanium and boron. Sterling silver of 92.5 per cent purity is also alloyed with platinum in some artistic settings to modify appearance, make it harder and increase tarnish resistance.