Hardness: 7.50
Refractive Index: 1.66-1.68
Specific Gravity: 3.25
Birthstone:
Astral Stone:
Anniversary Stone:
Origination: Sri Lanka, Myanmar & the United States.
Care & Cleaning: Clean with a soft polishing cloth, plain water rinse or mild solution of soap & water.
Fiction, Facts & Folklore:
Gem quality sillimanite crystals are quite rare and seldom seen at retail.
Sillimanite crystals show a most impressive pleochroism.
The blue variety of sillimanite is the most sought after and is found only in the ruby-rich Mogok region of Burma.
The gray to green variety comes from the gem gravels of Sri Lanka.
A third variety found in massive rock forms comes from the Clearwater River Valley in Idaho. This material is not considered to be gem quality, and is normally used in the creation of artifacts. This variety can also sometimes be found in the tiny state of Delaware.
Sillimanite is nearly always seen as a flat cut or en cabochon.
Because it is found with fibrous inclusions, sillimanite is sometimes known in the jewelry world as �fibrolite�.