Sterling silver is an alloy of silver containing 92.5% pure silver and 7.5% other metals, usually copper. The sterling silver standard has a minimum millesimal fineness of 925.

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 is generally discounted. The word could have derived from the Old English word "stiere", meaning "strong, firm, immovable".

Starling theory, discounted

Although marks of birds have been used in some coins of Edward the Confessor, sterling is not likely to have been derived from starling, as the word for starling at the time was spelled stær. If the coin had been named after the bird, it would have been called starling.

Mint mark theory

The 1955 edition of the Oxford English Dictionary states that the early Middle English name sterling was presumably descriptive of small stars that were visible on early Norman pennies. (Old English: steorling.)

"Easterling" theory

An alternative explanation put forth by Walter de Pinchebek circa 1300 is that sterling silver may have been known first as "Easterling Silver". The term "Easterling Silver" is believed to have been used to refer to the grade of silver that had originally been used as the local currency in an area of Germany, known as "The Easterling".