Amethyst, from the Greek word meaning "unbreakable", is chemically composed of SiO2.
It is a trigonal crystal system with hexagonal crystals with transverse lines, left and right forms, and bicrystals are common. Hardness 7. Crystals often contain irregular or plume-like gas-liquid inclusions. It is one of the most valuable members of the crystal family, because of its purple color due to the presence of Mn and Fe3+ in its crystals. It is transparent and has obvious polychromy when viewed under a dichroic mirror. Amethyst Strings

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