Silver is the cheapest precious metal and used in jewelry pieces of all kinds. Pure, or fine, silver is quite soft, so when used in jewelry pieces, silver is most commonly alloyed with another metal to add strength. 1

Alloy Fineness Composition
Fine Silver 999 > 99.9% Ag 1
Britannia Silver 958 > 95.8% Ag, Cu 1
Argentium Silver 935, 940, 960 > 93.5% Ag, Cu, Ge 2
Sterling Silver 925 > 92.5% Ag, Cu 1