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The carat (ct) is a unit of mass equal to 200 mg (0.2 g; 0.007055 oz) and is used for measuring gemstones and pearls. The current definition, sometimes known as the metric carat, was adopted in 1907 at the Fourth General Conference on Weights and Measures, and soon afterwards in many countries around the world.〔The United States adopted the metric carat definition on July 1, 1913, the United Kingdom on 1 April 1914.〕 The carat is divisible into one hundred ''points'' of two milligrams each. Other subdivisions, and slightly different mass values, have been used in the past in different locations. In terms of diamonds, a paragon is a flawless stone of at least 100 carats (20 g). The ANSI X.12 EDI standard abbreviation for the carat is CD.〔(State of Connecticut, Dept. of Admin. Services )〕 ==Etymology== First attested in English in the mid-15th century, the word ''carat'' came from Italian ''carato'', which came from Greek ''kerátion'' (κεράτιον) meaning carob seed (literally "small horn") and potentially from Arabic ''qīrāṭ'' (قيراط).〔(κεράτιον ), Henry George Liddell, Robert Scott, ''A Greek-English Lexicon'', on Perseus〕〔Walter W. Skeat (1888), ''(An Etymological Dictionary of the English Language )''〕 (diminutive of - ''keras'', "horn"〔(κέρας ), Henry George Liddell, Robert Scott, ''A Greek-English Lexicon'', on Perseus〕) and was a unit of weight〔(carat ), Oxford Dictionaries〕 though it was not likely used to measure gold in classical times.〔 The Latin word for carat is ''siliqua''. This common belief that carat derives from carob seeds stems from the assumption that the seeds had unusually low variability in mass. However, one group of researchers have found that carob seeds in fact have typical variability compared to the seeds of other species. This was not the only reason. It is said that, in order to keep regional buyers and sellers of gold honest, potential customers could retrieve their own carob seeds on their way to the market, to check the tolerances of the seeds used by the merchant. If this precaution was not taken, the potential customers would be at the mercy of "2 sets of carob seeds". One set of "heavier" carob seeds would be used when buying from a customer (making the seller's gold appear to be less). Another, lighter set of carob seeds would be used when the merchant wanted to sell to a customer. In the past, each country had its own carat. It was often used for weighing gold. Starting in the 1570s, it was used to measure weights of diamonds.〔 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「Carat (mass)」の詳細全文を読む スポンサード リンク
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