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Sterling silver is an alloy of silver containing 92.5% by mass of silver and 7.5% by mass of other metals, usually copper. The sterling silver standard has a minimum millesimal fineness of 925. ''Fine silver'', for example 99.9% pure silver, is generally too soft for producing functional objects; therefore, the silver is usually alloyed with copper to give it strength while preserving the ductility and appearance of the precious metal. Other metals can replace the copper, usually with the intention of improving 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. Alloys such as argentium silver have appeared in recent decades. ==Etymology== One of the earliest attestations of the term is in Old French form ''esterlin'', in a charter of the abbey of Les Préaux, dating to either 1085 or 1104. The English chronicler Orderic Vitalis (1075 – c. 1142) uses the Latin forms ''libræ sterilensium'' and ''libræ sterilensis monetæ''. The word in origin refers to the newly introduced Norman silver penny. According to the Oxford English Dictionary, the most plausible etymology is derivation from a late Old English ''steorling'' (with (or like) a "little star"), as some early Norman pennies were imprinted with a small star. There are a number of obsolete hypotheses. One suggests a connection with starling, because four birds (in fact martlets) were depicted on a penny of Edward I, and another, a supposed connection with ''easterling'', a term for natives of the Baltic, or the Hanse, towns of eastern Germany. This etymology is itself medieval, suggested by Walter de Pinchebek (ca. 1300) with the explanation that the coin was originally made by moneyers from that region.〔"sterling, n.1 and adj.". OED Online. December 2011. Oxford University Press. (Entry 189985 ) (accessed February 28, 2012).〕 The British numismatist Philip Grierson points out that the stars appeared on Norman pennies only for the single three-year issue from 1077-1080 (the Normans changed coin designs every three years), and that the star-theory thus fails on linguistic grounds: extensive research has been done on how coins acquire names, including nicknames. Grierson's proposed alternative involves an analogy with the Byzantine solidus, originally known as the ''solidus aureus'' meaning "solid gold" or "reliable gold". Even though English silver pennies were known for their consistent weight and purity in the days of Offa, King of Mercia, by the time of the Conquest English coinage had seriously degenerated. One of the first acts of the Normans was to restore the coinage to what it had been in the days of Offa, and to maintain it consistently. Grierson thus proposes that "sterling" derives from "ster"〔Fr. the ancient Greek στερεός () = 'solid'.〕 meaning "strong" or "stout". 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「sterling silver」の詳細全文を読む スポンサード リンク
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