February Birthstone - Amethyst

Physical and Chemical Properties

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Chemical composition

Amethyst usually is a transparent variety of quartz. Quartz in all varieties is Silicon Dioxide, SiO2. It has a specific gravity of 2.66, and it defines 7 on Mohs hardness scale. it has refractive indexes ranging from 1.544 to 1.553, it is uniaxial, positive, and may be strongly dichroic in several colored varieties.

Colors

Amethyst is transparent and comes in shades of purple. Some translucent to opaque amethyst is also found and the purplish zones alternate with white or grayish areas. Color zonation can be very intense in transparent, translucent and opaque varieties. The most desired hues ranged from deep purplish-red to purple-red and these stones were called Uralian or Siberian Amethyst, terms that are now color grades rather than source areas. These February Birthstones range from deep violet to pale purple and may appear evenly colored or in bands. The purple color comes from iron oxide, manganese, or hydrocarbon content.

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