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Wollastonite is a calcium inosilicate mineral (CaSiO3) that may contain small amounts of iron, magnesium, and manganese substituting for calcium. It is usually white. It forms when impure limestone or dolostone is subjected to high temperature and pressure sometimes in the presence of silica-bearing fluids as in skarns or contact metamorphic rocks. Associated minerals include garnets, vesuvianite, diopside, tremolite, epidote, plagioclase feldspar, pyroxene and calcite. It is named after the English chemist and mineralogist William Hyde Wollaston (1766–1828). Some of the properties that make wollastonite so useful are its high brightness and whiteness, low moisture and oil absorption, and low volatile content. Wollastonite is used primarily in ceramics, friction products (brakes and clutches), metalmaking, paint filler, and plastics. Despite its chemical similarity to the compositional spectrum of the pyroxene group of minerals—where magnesium and iron substitution for calcium ends with diopside and hedenbergite respectively—it is structurally very different, with a third SiO4 tetrahedron in the linked chain (as opposed to two in the pyroxenes). ==Production trends== World production data for wollastonite is not available for many countries and those that are available frequently are 2 to 3 years old. Estimated world production of crude wollastonite ore was in the range of 530,000 to 550,000 tonnes in 2010. World reserves of wollastonite were estimated to exceed 90 million tonnes, with probable reserves of about 270 million tonnes. However, many large deposits have not been surveyed yet.〔(Wollastonite ), ''USGS Mineral Commodity Summaries'' 2011〕 In 2010, the major producers were China (300,000 tonnes), India (120,000 t), United States (67,000 t), Mexico (30,000 t) and Finland (16,000).〔 Finland has long been a major European supplier of wollastonite, but in 2003 it was joined by Spain with comparable production volumes. In the United States, wollastonite is mined in Willsboro, New York and Gouverneur, New York. Deposits have also been mined commercially in North Western Mexico.〔Robert L. Virta (Wollastonite ), ''USGS 2009 Minerals Yearbook'' (October 2010)〕 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「wollastonite」の詳細全文を読む スポンサード リンク
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