Sterling Silver
The sterling silver standard has a minimum millesimal fineness of 925. Sterling is an alloy of silver containing 92.5 % pure silver and 7.5 % other metals, usually copper. more...
Fine silver (99.9% pure) is generally too soft for producing large functional objects; therefore, the silver is usually alloyed with copper to give it strength, while at the same time preserving the ductility and beauty of the precious metal. Other metals can replace the copper, usually with the intent to improve various properties of the basic sterling alloy such as reducing casting porosity, eliminating firescale, and increasing resistance to tarnish. These replacement metals include germanium, zinc and platinum, as well as a variety of other additives, including silicon and boron. A number of alloys have appeared in recent years, formulated to lessen firescale or to inhibit tarnish, and this has sparked heavy competition among the various manufacturers, who are rushing to make claims of having the best formulation. However, no one alloy has emerged to replace copper as the industry standard, and alloy development is a very active area.
Origin of the alloy metal
Although there is much confusion over the origin of the word "sterling", there is general agreement that the sterling alloy originated in what is now continental Europe, and was being used for commerce as early as the 12th century in the area of what is now northern Germany.
Origin of the word "sterling", used to refer to the silver alloy
The word "sterling", used in reference to the 0.925 grade of silver, emerged in England by the 13th century. The terms "sterling" and "pound sterling", acquired their meaning in more than a century, and from convergent sources. There are three possible origins for the word "sterling", two originate from 12th and 13th century coinage, and one generally discounted, moreover, the word could have derived from the Old English word "stiere", meaning "strong, firm, immovable".
Read more at Wikipedia.org