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The mineral heliotrope, also known as bloodstone, is a form of chalcedony (which is a cryptocrystalline mixture of quartz and its monoclinic polymorph moganite). The "classic" bloodstone is green chalcedony with red inclusions of iron oxide or red jasper. Sometimes the inclusions are yellow, in which case the mineral is given the name plasma. The red inclusions are supposed to resemble spots of blood; hence the name "bloodstone". The name "heliotrope" (from Greek ἥλιος ''helios'', Sun, τρέπειν ''trepein'', to turn) derives from various ancient notions about the manner in which the mineral reflects light. These are described, e.g., by Pliny the Elder (''Nat. Hist.'' 37.165). Heliotrope features in one of Boccaccio's stories in the ''Decameron''. Heliotrope is sometimes used in carved signet rings and is the traditional birthstone for March. ==Sources== The primary source of the stone is India. It is also found in Brazil, China, Australia, and the United States. There is also an outcrop of bloodstone on the Isle of Rum, in Scotland. 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「Heliotrope (mineral)」の詳細全文を読む スポンサード リンク
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