Cochise College           Student Papers in Geology

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Roger Weller, geology instructor

by KaMari Craft
Physical Geology
Fall 2011



     Have you ever wondered what your birthstone was ? What different birthstones there were in this world ? Well I have always wondered that . My birthstone happens to be topaz . Topaz , also known as citrine can be a yellowish , orange color , or it can come in a beautiful blue color . Topaz is a silicate mineral .





chemical formula : Al2SiO4(F,OH)2

Strunz classification : 9.AF.35

crystal symmetry: Orthohombric dipyramidal

H-M symbol: (2/m 2/m 2/m)

Space group: Pbnm

Unit Cell : a=4.65 A, b = 8.8 A,

c=8.4 A , Z=4





colorless (if no impurities) , blue, brown , orange , gray , yellow, green , pink and reddish pink.

Crystal Habbit: Prismatic crystals with faces striated parallel to long dimension; also columnar, compact , massive .

Crystal system: Orthorhombic

Cleavage:  [001] Perfect

Fracture: Subconchoidal to uneven

Mohs scale (hardness) : 8 ( defining mineral)

Luster : Vitreous

Streak: white

Diaphaneity: Transparent

Specific gravity: 3.49-3.57

Optical properties: Biaxial(+)


     Topaz of any type is a good jewelry stone and is historically one of the most important gemstones. With its relatively high refractive index and hardness of eight (Mohs scale) , with no special sensitivity to chemicals it can be used , with appropriate care (should be protected from hard knocks) , in any jewelry application . Topaz comes in many colors including clear , brown , yellow , orange , red , pink, and blue . The blue topaz , with a pale to medium blue color created by irradiation , can be found in very large sizes at affordable prices . the fine golden-yellow variety , known as Imperial Topaz , is relatively scarce. Topaz colors are rarely vivid . The most common color is yellow with red tint ; the most valuable pink to reddish . The coloring agents are iron and chromium .



     The name Topaz is most probably derived from an island in the Red Sea , " Topazos " , today called Zabargad , the ancient source of peridot . In former times , all golden-brown and sometimes also green gemstones were called topaz , which caused sufficient confusion such that today real topaz is referred to as precious topaz .


     Topaz is the birthstone for those who are born in the month of November .

golden topaz- photo courtesy of R.Weller/Cochise College

imperial topaz- photo courtesy of R.Weller/Cochise College

blue topaz pendant- photo courtesy of R.Weller/Cochise College







     During the Middle Ages , topaz was thought to heal both physical and mental disorders and prevent death . The Greeks believed it had power to increase strength and to make its wearer invisible while the Romans believed it had power to improve eyesight . The Egyptians wore it as an amulet to protect them from injury .