Topaz is a nesosilicate, Al2[(F,OH)2/SiO4], and 8 on the hardness scale. It is in the orthorhombic crystal system, which is reflected in the commonly found prismatic crystal form with orthorhombic pyramid terminations. It has perfect basal cleavage, as well as a conchoidal and uneven fracture. Topaz is transparent and translucent, with a vitreous luster, and high specific gravity, 3.49-3.57. It is doubly refractive, 1.609-1.643, with a strong to definite pleochroism (with the exception of blue topaz, which as weak to none), and weak fluorescence. When topaz is gently heated or rubbed, it becomes electrically charged. Topaz occurs in cavities within granite or rhyolite igneous rock, pegmatite dikes, high temperature quartz veins, and/or alluvial deposits ( The Mineralogy Database). Inclusions are tear-shaped cavities. Read about mining from, Topaz Visiting the Mine, http://www.secretsofthegemtrade.com/articles_11.htm, an excerpt from R. Wise, Secrets of the Gem Trade.
In times past, all yellow, golden brown, and sometimes green gems were called topaz. Topaz may be colorless, yellow, red-brown, light blue, pink-red, red, violet, and light green. The most common color is yellow with a reddish tint, while the most valuable color is pink to reddish-orange. This pink to reddish-orange is referred to as Imperial topaz. A red-brown topaz is called rootbeer topaz and is more expensive than citrine quartz, but less expensive than morganite beryl (theimage.com). Some yellowish-brown topaz will fade in sunlight and natural blue topaz is fairly rare.
 Topaz from Topaz Mountain, Utah from The Image |
 Topaz from Thomas Mountain, Utah taken from The Image |
 Rootbeer topaz taken from The Image |
 Blue topaz taken from The Image |
 Carved blue topaz The Image |
 Image from former website Mineral and Gemstone Kingdom |
 Clear or white topaz with rutile, taken from The Image |
 Clear or white topaz with rutile, taken from The Image |
 Close up of rutile taken from The Image |
Topaz is the November birthstone and the 4th anniversary gem. For more details, visit Jewelry Central.
Synthetic blue topaz has been on the market since 1976 and some clear to yellowish topaz will turn to various shades of blue with heat or irradiation treatments. Topaz is often imitated by varieties of quartz. Yellow heat treated amethyst and citrine quartz have been known by the trade names such as Gold topaz, Madeira topaz, False topaz, Brazilian topaz, Citrine topaz, whereas brown to black quartz has been called Smoky topaz. Quartz is often substituted for topaz as a birthstone in jewelry, many people would not recognize the natural topaz. The term Imperial topaz and Precious topaz are both referring to topaz, but Oriental topaz is golden sapphire.  Imperial topaz taken from The Image |
Return to the Syllabus or choose another gemstone below.
| Alexandrite | Amber | Amethyst | Chalcedony | Diamond | Emerald | Garnet | Jade | Malachite | Opal | Pearl | Peridot | Ruby | Sapphire | Tanzanite | Topaz | Tourmaline | Turquoise | |
This page originates from the Earth Science department for the use and benefit of students enrolled at Emporia State University. For more information contact the course instructor, S. W. Aber, e-mail: saber@emporia.edu Thanks for visiting! Webpage created: November 5, 2000; last update: March 9, 2008.
Copyright 1999-2008 Susan Ward Aber. All rights reserved.