Sillimanite

Sillimanite is formed from aluminum silicate and is a transparent to translucent mineral ranging from white to gray, brown and green. For its fibrous inclusions, it is sometimes also known as "fibrolite" in the jewelry world. Gem quality sillimanite crystals are rare and is seen seldom at retail.Sillimanite is basically used to manufacture mullite refactory ceramics, spark plugs, and high temperature crucibles. For jewelry, the chatoyant green and blue varieties are most suitable.