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Sillimanite Gemstone

Sillimanite (also  known  as  Fibrolite) is  found  in  various  colours  including  green,  yellow, brown, blue, white and even black. It is a ‘polymorph’ with two other minerals, Kyanite and  Andalusite,  which  simply  means  that  it  shares  the  same  chemistry  but  has  a  different crystal structure.

Like Kyanite, this precious stone has a brittleness  and directional cleavage that makes it difficult to facet. The scarcity of Sillimanite, combined with the difficulty in cutting it, adds incredible value to this gem once it has been successfully faceted.

The  gem  is  a  complete  Jekyll  and  Hyde;  it  can be discovered as a truly transparent gem,  or completely opaque with a waxy lustre. The  gem’s name was given in memory of geologist  Benjamin Silliman.

It  appears  in  deposits  in  several  countries  including Tanzania, South Africa, Korea, India,  Madagascar,  England  and  the  USA.  The  rare  transparent variety is mined in the Mogok Valley,  Burma, where the deposit has also yielded some  extremely rare violet-blue gems.

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