THE GOLD OF THAT LAND: Biblical Minerals & Rocks  


 

65.     topaz 

Hebrew: pitd‚w. Exodus 28:17, 39:10; Job 28:19; Ezekiel 28:13.

Greek: topazion, from Topazos, Pliny's "Topaz Island," now known as Zabargad (Zebirget), in the Red Sea. Revelation 21:20.

Probable Identification:

    Biblical topaz is peridot or gem olivine, which is also known today as chrysolite. See "CHRYSOLITE."

Mineralogy:

    Topaz in modern usage is an aluminum fluorosilicate [Al2SiO4(F2-xOH)x] which forms striated orthorhombic prismatic crystals with dipyramidal terminations. Crystals have a vitreous luster, are transparent or translucent, and range in color from clear to yellow, pink, green, and blue, with yellow being the most popular. The physical properties of topaz vary with its fluorine/hydroxyl ratio. Topaz has a hardness of 8 and its specific gravity ranges from 3.50 to 3.57 in direct proportion to its fluorine content. Although harder than quartz, topaz cleaves so easily that gems require careful handling.

    Topaz crystallizes from gaseous fluorine-rich emanations during the last stages of igneous intrusions, where it occurs in pegmatite dikes, granite, or rhyolite lavas in association with tourmaline, fluorite, apatite, cassiterite, beryl, quartz, mica, and feldspars. Topaz crystals often serve as indicators of cassiterite deposits, and early tin miners may have produced topaz as a by-product. Gem topaz may be colorless, wine yellow, pink, red, pale blue, or a golden brown. The "Imperial topaz" mines near Ouro Preto in Minas Gerais, Brazil have produced golden to reddish-orange topaz known as "Brazilian rubies," and mines in Minas Gerais produce the finest blue topaz. Certain colors are unstable in sunlight, and heating alters yellow Brazilian topaz to pink. Topaz crystals often grow to large sizes. Although topaz has a Mohs scale hardness of 8, its cleavage makes it less desirable for gemstones.

    The Minas Gerais district of Brazil produces the most and finest of the world's precious topaz. The topaz deposits at Ouro Prieto were deposited by hydrothermal solutions that mineralized fault and fracture zones in the Piracicaba Group, which comprises the upper 1000 to 2000 meters of the Minas Series of ancient metamorphic rocks. Other sources are Australia, Burma, Ceylon, Germany, Mexico, Nigeria, Pakistan, Siberia, Ukraine, the United States, and Zimbabawe.

    "Indian topaz" is citrine, the yellow variety of quartz.

Historical Background:

    The Egyptians made the earliest known use of topaz during the period 1580-1350 BC, though it must have been known from tin and copper mining at least a thousand years earlier. Attractive topaz crystals were common. Greek and Roman lapidarists left us very few examples of engraved topaz because its cleavage made it difficult for them to engrave.

    Sources:

Hoover, D.B., 1992. Topaz. Oxford: Butterworth-Hienemann Ltd.

Hurlbut, 1952, op. cit.; 393-394.

Ralph, Jolyon, 1993-2004. http://www.mindat.org/min-3996.html

Schumann, op. cit.; 102-103.


       HOME            Introduction & Contents          List & Key        Appendices & References      News Items
 Copyright 2004, 2005, 2006 by Richard S. Barnett, Virtual Curator of Biblical Geology.
All rights reserved. This site is authored by Richard S. Barnett.
All contents belong to Richard S. Barnett. Reproduction of this site, in whole or in part, is prohibited without written permission.

For problems or questions regarding this Web site contact [Curator@biblicalgeology.com].
Last updated: 05/13/06.