Sillimanite Value, Price, and Jewelry Information
The fibrolite from Burma and Sri Lanka is well known to gem collectors, and highly prized because of its great scarcity. Blue and greenish gems are lovely, although very difficult to cut. Chatoyant material sometimes yields catseye fibrolites, which are also very rare. The material from Kenya is just as attractive as Burmese fibrolite but seems to be somewhat smaller in size.
SILLIMANITE (=FIBROLITE) Trimorphous with Kyanite, Andalusite.
Optics: a =1.654-1.661 β= 1.658-1.662; γ= 1.673-1.683.
Biaxial (+), 2V: 21—30°.
Occurrence: A mineral of metamorphic rocks, such as schists and gneiss; also granites.
Idaho; South Dakota; Oklahoma; Pennsylvania; New York; Connecticut; Delaware; North Carolina; South Carolina.
Canada; Ireland; Scotland; France: Germany; Czech Republic; Slovakia; Brazil; India; Madagascar; North Korea; South Africa; Tanzania.
Sri Lanka and Burma: green, blue. violet—blue facetable material; also from Sri Lanka, grayish green, chatoyant fibrolite.
Kenya: facetable crystals, pale bluish color to colorless, S.G. 3.27.
Comments: The fibrolite from Burma and Sri Lanka is well known to gem collectors, and highly prized because of its great scarcity. Blue and greenish gems are lovely, although very difficult to cut. Chatoyant material sometimes yields catseye fibrolites, which are also very rare. The material from Kenya is just as attractive as Burmese fibrolite but seems to be somewhat smaller in size.
Name: After Benjamin Silliman, mineralogist, of Yale University. Fibrolite is in allusion to the fibrous nature of this variety.
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