Charoite (thing)

A stone [K₅Ca₈(Si₆O₁₅)₂(Si₂0₇) Si₄O₉(OH) ·H₂O] typically found in the Chara River area in Russia. Because of its beautiful coloring, it is usually used for making jewelry.

Chemical Composition:

    Potassium  3.80 %  K         12.88 % K2O  
    Calcium   17.53  %  Na       24.53 % Na2O  
    Hydrogen   0.39 %  H          3.45 % H2O 
    Silicon   32.78 %  Si        59.14 % SiO2  
    Oxygen    43.75 %  O  
              ______             ______  
             100.00 %           100.00 % = Total Oxide

Usually purple or light brown in color, Charoite is found in distinctively fibrous, fine grained forms and tiny-crystal druse on its host rock. With a density of 2.54 - 2.58 and a hardness 5.0 - 6.0, the stone is usually found in a syenite massif, in metasomatic rocks.

The stone has a Dana class of 70.1.2.3, in the Double crankshaft chain subgroup, with inosilicate column or tube structures . A very rare stone, it is highly prized for it's rich purple colors for cabs.

The highest quality pieces are opaque, and can be effectively used in jewelry. Like Sugilite, it looks beautiful set with lapis lazuli or other such blue stones as well as many others.

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Source:

http://webmineral.com/data/Charoite.shtml - Contains excellent further information on optical and physical properties of the substance.