Crystal stone is hard, so it won't break easily. The hardness of rock crystal is 7, which is Mohs hardness, which is equivalent to the hardness of steel file. The relative density is 2.56 to 2.66 grams per cubic centimeter.

Rock crystals are clear and transparent, often containing cloud, star or flocculent gas-liquid inclusions, and often with microcracks. In addition, the rock crystal is polarized, and twin phenomenon can be seen. Crystal stone feels cold and glass feels warm.

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Crystal is mainly produced in pegmatite veins or caves, and crystal minerals are produced almost all over the world. The famous producing areas are Minas and Gila in Brazil, Madagascar and Arkansas in the United States, Urals and Myanmar in Russia.

China is rich in crystal resources, with crystal production in more than 25 provinces. Jiangsu is the main producer of high-quality crystals in China, among which Donghai Crystal is the most famous, and it is called "Crystal Capital of China". In addition, Hainan, Sichuan and Xinjiang are also the producing areas of high-quality crystals.

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