Aluminosilicate Mineral Profile Mineral Name: Sillimanite Chemical Formula: Al2SiO5 Silicate Structural Class: Nesosilicate Diagnostics Properties: <Tab/> Colour: White, Brown and Green Transparency: Transparent to Translucent Lustre: Silky or Vitreous <Tab/>Specific Gravity: 3.2 Streak: White Mohs Hardness: 7.5 in large crystals <Tab/>Mineral Cleavage: Perfect. Good in 1 direction lengthwise Occurrence: <Tab/> Type of Rock: Aluminium-rich metamorphic rocks <Tab/&…
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…gt;Geographic Localities: Brazil, England and other European sites Main Uses: Sillimanite is mainly used in the manufacture of spark plugs and other forms of ceramic insulation. It can be used as a gemstone although this is rare and is more often used as mineral specimens. Sillimanite: A compact chunk with obvious crystalline tendencies. Fibres are slightly curved and have a pearly lustre. (http://mineral.galleries.com/scripts/item.exe?ENLARGE+Minerals+Silicates+Sillimanite+SIL-1)