January Birthstone - Garnet;

Physical and Chemical Properties

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Chemical composition of Garnet

Garnet is a rather complex mineral that has a general chemical formula of R3R2(SiO4)3, where R3 is a bivalent (gives up two electrons) metal and R2 is a trivalent (gives up three electrons) metal when forming a chemical bond. The metal R3 may be Calcium (Ca++), Magnesium (Mg++), ferrous Iron (Fe++), or Manganese (Mn++), and the metal R2 may be Aluminum (Al+++), ferric iron (Fe+++), or Chromium (Cr+++). The hardness may vary from about 6 ½ to 7 ½ on the MOHS scale, and the specific gravity (S. G.) (weight of the stone compared to the weight of an equal volume of water) may vary from about 3.5 to 4.3. Garnets actually consist of a family of minerals that are silicate mixtures of magnesium, iron, and aluminum. Varieties include rhodolite ( the variety commonly accepted as the January birthstone), malaya, demantoid, grossular, hessonite, spessartite, hessonite, almandine, mandarin, and combinations between these varieties.

Colors of Garnet

The single garnet crystal may include a hodge-podge of elements, and garnets may be a multitude of colors; natural garnets are known in every color but blue. The luster of garnets ranges from vitreous to resinous to subadamantine. Colors can be red, brown, yellow, orange, white, green, or black or shades in between. Pyrope (bright red), rhodolite (pink-red), and almandine (violet-red) garnets tend to be the most common and popular colors. The spessartine garnet tends to be orange-red or brownish yellow.Other varieties of garnets are yellow, green, black, and even colorless. They may be translucent or slightly opaque.

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