Nouveautés Paires Lots Bijoux Contact
 
: Pierres précieuses Sillimanite
Sillimanite Gemstones
Sillimanite Crystal
Sillimanite Crystal

Sillimanite is a type of aluminum silicate that is related to both andalusite and kyanite. In fact, these three minerals are polymorphs - they share the same chemical composition but have different crystal structures. Kyanite is formed in a lower temperature and higher pressure environment, while andalusite forms at lower temperature and lower pressure conditions. Sillimanite forms at higher temperatures and higher pressures.

Sillimanite is named after the American chemist, Benjamin Silliman (1779-1864). Silliman was one of the first American professors of science and taught at Yale University. He was originally trained as a lawyer and taught law at Yale. The president of the university proposed that Silliman study chemistry and natural history, and then assume a new professorship in the sciences at Yale. Silliman thus became an important chemist and geologist and discovered the constituent elements of many minerals. He was also the very first person to distill petroleum.

Sillimanite Cat's Eye
Sillimanite Cat's Eye

Sillimanite has a hardness of 6.5 to 7.5 on the Mohs scale and a vitreous to silky luster. It has a refractive index of 1.655 to 1.684; approximately the same as that of spodumene. Its specific gravity is 3.23 to 3.27, placing it between apatite and diopside on the density scale. Like diamond, topaz and fluorite, sillimanite has perfect cleavage.

Sillimanite occurs in a number of colors, ranging from colorless to gray-white, yellowish, brownish and bluish. Sillimanite is rarely transparent. Sillimanite also occurs in a fibrous form sometimes known as fibrolite, so named because the mineral appears like a bunch of fibres twisted together. Some of this fibrous sillimanite displays chatoyancy (the cat's eye effect), often in an attractive violet-brown shade.

Throughout history, sillimanite has been considered a rare gemstone that is known mainly to collectors. Deposits of sillimanite have been found in Burma, Sri Lanka, Kenya and the USA. Recent finds in India have made sillimanite more widely available, though it is still classified as a collector's gem.

  • Première publication: February-10-2009
  • Dernière mise à jour: August-22-2017
  • © 2005-2017 GemSelect.com tous droits réservés.
    Reproduction (texte ou graphique), sans le consentement écrit de GemSelect.com (SETT Company Ltd) est strictement interdite.
Support à la clientèle en parlant d'anglaise seulement

Sans frais - USA et Canada seulement:
1-800-464-1640

International:
+66-39303404

Réorganiser les articles

Économisez de l'argent
Pas de frais d'expédition pour les articles supplémentaires!
$ 6,99 Livraison dans le monde

Update Translation
 
Current Value
New Value

Creating Account...

Close window to continue

Facebook did not provide your email to login.

Please allow Facebook to provide your email or sign up an account with GemSelect.

GemSelect Gemstones
X Fermer la fenêtre
Colored Gemstones
X Fermer la fenêtre
Colored Gemstones
X Fermer la fenêtre
Colored Gemstones
Taille et poids

Gems are always measured in Millimeter (mm)

Dimensions are given as;
length x width x depth,
except for round stones which are;
diameter x depth

Select gems by size, not by weight!
Gem varieties vary in density, so carat weight is not a good indication of size

Note: 1ct = 0.2g

Size Comparison Chart