World Library  
Flag as Inappropriate
Email this Article

Texas blue topaz

Article Id: WHEBN0019480542
Reproduction Date:

Title: Texas blue topaz  
Author: World Heritage Encyclopedia
Language: English
Subject: List of U.S. state minerals, rocks, stones and gemstones, List of Texas state symbols
Collection:
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Texas blue topaz

This article is about the mineral or gemstone. For other uses, see Topaz (disambiguation).
Topaz
crystals on matrix
General
Category Silicate mineral
Formula
(repeating unit)
Al2SiO4(F,OH)2
Strunz classification 9.AF.35
Crystal symmetry Orthorhombic dipyramidal
H-M symbol: (2/m 2/m 2/m)
Space group: Pbnm
Unit cell a = 4.65 Å, b = 8.8 Å,
c = 8.4 Å; Z = 4
Identification
Color Colorless (if no impurities), blue, brown, orange, gray, yellow, green, pink and reddish pink
Crystal habit 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 (+)
Refractive index nα = 1.606–1.629
nβ = 1.609–1.631
nγ = 1.616–1.638
Birefringence δ = 0.010
Pleochroism Weak in thick sections X = yellow; Y = yellow, violet, reddish; Z = violet, bluish, yellow, pink
Other characteristics Fluorescent, short UV=golden yellow, long UV=cream
References [1][2][3][4]

Topaz is a silicate mineral of aluminium and fluorine with the chemical formula Al2SiO4(F,OH)2. Topaz crystallizes in the orthorhombic system, and its crystals are mostly prismatic terminated by pyramidal and other faces.

Color and varieties

Pure topaz is colorless and transparent but is usually tinted by impurities; typical topaz is wine, yellow, pale gray, reddish-orange, or blue brown. It can also be made white, pale green, blue, gold, pink (rare), reddish-yellow or opaque to transparent/translucent.

Orange topaz, also known as precious topaz, is the traditional November birthstone, the symbol of friendship, and the state gemstone of the US state of Utah.[5]

Imperial topaz is yellow, pink (rare, if natural) or pink-orange. Brazilian Imperial Topaz can often have a bright yellow to deep golden brown hue, sometimes even violet. Many brown or pale topazes are treated to make them bright yellow, gold, pink or violet colored. Some imperial topaz stones can fade on exposure to sunlight for an extended period of time.[6][7]

Blue topaz is the state gemstone of the US state of Texas.[8] Naturally occurring blue topaz is quite rare. Typically, colorless, gray or pale yellow and blue material is heat treated and irradiated to produce a more desired darker blue.[7]

Mystic topaz is colorless topaz which has been artificially coated giving it the desired rainbow effect.[9]

Localities and occurrence


Topaz is commonly associated with silicic igneous rocks of the granite and rhyolite type. It typically crystallizes in granitic pegmatites or in vapor cavities in rhyolite lava flows like those at Topaz Mountain in western Utah. It can be found with fluorite and cassiterite in various areas including the Ural and Ilmen mountains of Russia, in Afghanistan, Sri Lanka, Czech Republic, Germany, Norway, Pakistan, Italy, Sweden, Japan, Brazil, Mexico; Flinders Island, Australia; Nigeria and the United States.

Some clear topaz crystals from Brazilian pegmatites can reach boulder size and weigh hundreds of pounds. Crystals of this size may be seen in museum collections. The Topaz of Aurangzeb, observed by Jean Baptiste Tavernier measured 157.75 carats.[10] The American Golden Topaz, a more recent gem, measured a massive 22,892.5 carats.

Colorless and light-blue varieties of topaz are found in Precambrian granite in Mason County, Texas[11] within the Llano Uplift. There is no commercial mining of topaz in that area.[12]

Etymology


The name "topaz" is derived (via Old French: Topace and Latin: Topazus) from the Greek Τοπάζιος (Τοpáziοs) or Τοπάζιον (Τοpáziοn),[13] the ancient name of St. John's Island in the Red Sea which was difficult to find and from which a yellow stone (now believed to be chrysolite: yellowish olivine) was mined in ancient times; topaz itself (rather than topazios) was not really known about before the classical era. Pliny said that Topazos is a legendary island in the Red Sea and the mineral "topaz" was first mined there.

The word topaz is related to the Sanskrit word तपस् "tapas" meaning "heat" or "fire",[13] and also to the Hebrew word for "orange" (the fruit): tapooz (תפוז), both of which predate the Greek word.

Historical usage

Nicols, the author of one of the first systematic treatises on minerals and gemstones, dedicated two chapters to the topic in 1652.[14] In the Middle Ages, the name topaz was used to refer to any yellow gemstone, but in modern times it denotes only the silicate described above.

Many modern English translations of the Bible, including the King James Version mention topaz in Exodus 28:17 in reference to a stone in the Hoshen: "And thou shalt set in it settings of stones, even four rows of stones: the first row shall be a sardius, a topaz, and a carbuncle (garnet): this shall be the first row."

However, because these translations as topaz all derive from the Septuagint translation topazi[os], which as mentioned above referred to a yellow stone that was not topaz, but probably chrysolite (chrysoberyl or peridot), it should be borne in mind that topaz is likely not meant here.[15] The masoretic text (the Hebrew on which most modern Protestant Bible translations of the Old Testament are based) has pitdah as the gem the stone is made from; some scholars think it is related to an Assyrian word meaning "flashed".

More likely, pitdah is derived from Sanskrit words (पीत pit = yellow, दह् dah = burn), meaning "yellow burn" or, metaphorically, "fiery".

References

External links

  • Pink Topaz, Biblical Topaz References Farlang – gem information and full text historical references
  • Topaz and other minerals found at Topaz Mountain, Juab County, Utah Geological Survey
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 



Copyright © World Library Foundation. All rights reserved. eBooks from World Library are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.