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Chemical name Aluminum silicate fluoride hydroxide
Chemical formula Al2SiO4(F, OH)3
Colors Colorless, white, pale blue, light green, yellow, yellowish brown, or red
Crystal habit Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).
Crystal system Orthorhombic
Cleavage Perfect (001)
Fracture Irregular/Uneven, Sub-Conchoidal
Hardness 8
Name origin Named after Topasos Island in the Red Sea. In antique times, the name was probably used for the gemstone that is now known as peridot.
Specific gravity 3.5 - 3.6, Average = 3.55
Streak White

Topaz is one of the hardest minerals rating an 8 on the Mohs hardness scale. Chemically, topaz is Aluminum silicate fluoride hydroxide Al2SiO4(F, OH)3 and is classified as a silicate. It is commonly used as a gemstone and its crystals can grow to a very large size. Topaz is commonly a shade of yellow or orange, but may also be colorless and is found in the blue and green ranges. Topaz is the birthstone for November.


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