Facts About the Mineral Topaz

Topaz is a semi-precious stone used primarily in jewelry, especially as the birthstone for November. Topaz is an igneous mineral and is only found in areas that experienced volcanic activity. The most common varieties range in color from yellow to brown.

Chemical Composition

Topaz is primarily composed of the mineral aluminum fluorosilicate. The chemical formula is Al2SiO4(F, OH)2. A range of other elements can also occur in topaz in small quantities and these impurities give the stone its color.

Hardness

Topaz has a Mohs hardness score of 8 and it is one of the original reference samples for the Mohs scale. When scratched by a harder mineral, topaz streaks white.

Color

Although topaz is typically thought of as yellow, pure topaz is clear and colorless. Any color the stone has comes from additional elements incorporated into the mineral's crystalline structure. Yellow and brown are the most common colorations, but other possible colors include white, pink, peach orange and even red. Blue topaz, the official gemstone of Texas, can also occur but is rare and typically pale.

Synthetic Topaz

Most synthetic topaz is made by entirely artificial means. Synthetic topaz is potentially purer than the naturally occurring mineral, so impurities are carefully added to obtain the desired color and clarity. This type of topaz should always be labeled synthetic or laboratory produced. "Mystic topaz" refers to any form of topaz, natural or synthetic, that has a thin iridescent coating of titanium oxide. Since the coating is an artificial enhancement, mystic topaz is also labeled synthetic.

History

In antiquity, the word "topaz" could refer to nearly any yellow gemstone. During the Middle Ages, the term narrowed to refer only to the yellow stone we now know as topaz. The name refers to a Greek island known in antiquity as the source for a yellow stone that may or may not have been topaz.

References

• Mineral Gallery: The Mineral Topaz
• Mineral Miners: Topaz Mineral Information Page
• "The Illustrated Bead Bible: Terms, Tips & Techniques"; Theresa Flores Geary and Debra Whalen; 2008
• Geology.com: Topaz