Silver Purity & Composition
Due to its high level of inherent softness, pure silver is actually too malleable to be used alone in jewelry making-it is easily dented and scratched when exposed to daily wear and tear. Instead, silver is typically mixed with other alloy metals.
In its pure form silver is almost as soft as gold, and therefore is usually alloyed with copper for strength. Karatage is not marked because, legally, anything called "silver" or "sterling silver" is 92.5% pure.
Purity of silver is based on the other metals, which are available in the silver in the form of metal alloys. Unlike gold, but like platinum, silver purities are expressed as units of a 1,000 parts. On the basis of its purity, it can be described as below:
Pure / Fine Silver ...
Britannia Silver - has 95.8% silver purity.
(see full article on Sterling Silver)
Bronze - Bronze is made from copper, alloyed primarily with tin and zinc. Bronze is a hard metal with a high-wear resistance. Bronzes (like gold) can come as yellow bronze, red bronze, and white bronze.
See also: What is the meaning of Rough, Gold, Purity, Jewelry, Sterling silver?