| Physical Geology 2003 |  |
CONTENTS
Introduction
Physical Characteristics
Geological process
Products of the
geological process
Impacts
Aztec
mosaic of the goddess Quetzalcoatl
This
thin section shows the transparency of turquoise.
Figure 1
Such crystals are seen through a microscope.
Related
Links
Rockhounding
Arkansas
Mineralogy Database
The
Mineral Galleries
Mineralogical Society
of America
TURQUOISE:
Not just an accessory
Did you know Turquoise
is a mineral?
Introduction
Turquoise
in chemical terms is copper hydroxi phosphate.
Sometimes referred to as Callaite, this mineral from the phosphate class
ranges in color from blue to medium green. (www.webmineral.com)
As seen in the variety of theses samples,
greener turquoise contains more Fe (iron) and has been subjected to
more moisture. (http://ist-socrates.berkely.edu/~eps2/wisc/Lect16html
and www.americana.net/tourq.html)
Also
known as "turkish stone", the word turquoise is a French word
that
means "stone of Turkey". Reflecting this mineral's long history
as
a valuable ornament, Turkey was not only a location where turquoise
was mined
but also part of a trade route used to bring this mineral to Europe.
Turquoise
has been mined as early as 6000 BC, and is one of the most valuable
non-transparent minerals. Over time it has had ornamental use across
the globe, and was very important for the first peoples of North and
South American. Prehistoric Native Americans mined turquoise for ornamental
use. The Zuni Indians,have been inhabitants of what is currently New
Mexico for thousands of years, and are well known for their turquoise
jewelry. (http://www.pe.net/~rksnow/nmcountyzunipueblo.htm ,www.americana.net/tourq.html,
www.ist-socrates.berkely.edu/~eps2/wisc/Lect16.html and http://mineral.galleries.com)
Aztec
Turquoise Mosaic of the two headed serpent.
Physical
Characteristics
As
a Hydrated Copper Aluminum Phosphate mineral, turquoise is composed
of aluminum, copper, phosphorus, hydrogen and oxygen. Turquoise is an
example of a typical phosphate as it is often strongly colored and average
in hardness (www.theimage.com and www.mineral.galleries.com)
Strike:
White
Hardness: 5-6
Luster: Dull to Waxy
Transparency: semi-transparent to opaque (FIGURE 1)
Crystal Habits: Crystals rarely visible without microscope
Fracture: Conchoidal and smooth
Cleavage: Perfect in 2 directions, rarely seen.
Specific Gravity: 2.6-2.9
Chemistry: CuA16(P0 4)4(OH)8 4H20
CLASS: PHOSPHATES
(Perkins p472, http://webmineral.com/data/turquoise.shtml and http://mineral.galleries.com)
Geologic
Processes of
Copper Hydroxi Phosphate
The mineral forms in association with copper deposits, or in
other words it forms as a secondary mineral. Copper transported in water
interacts with
phosphorous and aluminum-bearing rocks.
Turquoise is associated with Al-rich (aluminum rich) volcanic
rocks association with copper deposits. The majority of turquoise
is found in regions with volcanic or thermal history. Most turquoise
forms in locations where magmatic solutions have intruded into fractures
or pores.
Immense heat and chemical changes between the protolith and new rock
are other necessary conditions. After this process, chemical weathering
(water solutions and air) over a long period of time allows the mineral
to form.
Finally, the mineral forms when the chemical compound CuA16(P0
4)4(OH)8 4H20 dissolves into water that has been deposited into veins,
seams, stringers and crusts. (Perkins and www.ist-socrates.berkely.edu/~eps2/wisc/Lect16.html)
Turquoise of blue and blue-green can be found in large amounts
at Mount Ali Mirsai in Iran. The mineral is also found in Arizona, Nevada
and New Mexico, US; Australia; Iran; Afghanistan and other areas of
the Middle East. (Novak 1999 and http://mineral.galleries.com)
Products
of the Geologic Process
Iron
pyrites and sometimes bits of quartz create blotches and dark lines
found in many turquoise specimens.
Quality
turquoise can be sold by the piece, and then the remainder is sold or
processed for sale by weight.
Turquoise
that is hard, dense and with an inherent luster can be cut, shaped and
polished directly after being mined, without any additives.
Other turquoise must be stabilized with a resin or treated
to improve color. (http://www.admmr.state.az.us/minupdat99.htm and http://turquoise-amber.com/history_of_turquoise.html)
Impacts
Mass-market
mining of turquoise as a gemstone or by-product has had large impacts.
Though it has been mined for thousands of years, unfortunately this
resource is in shorter supply as the demand for it has increased.
Because turquoise is a valuable and nonrenewable ore resource, the demand
for this gemstone will only increase with restricted production. For
example, in Arizona, turquoise is still the most important gemstone
being produced. However, as Arizona's resources have become exhausted,
Arizona's Morenci Mine and the deposits at Bisbee are producing very
little. (http://www.admmr.state.az.us/minupdat99.htm)
According Professor Johnson at Northern Kentucky University, there are
only 3 working mines in the USA are currently producing gem grade turquoise.
(http://www.nku.edu/~johnsonsa/Course%20Lectures/Earth%20Resources.htm)
IN
CONCLUSION,
Synthetic turquoise jewelry may not be ascetically pleasing.
However, if mining continues at today's rate, “fake” turquoise
may someday become our
only reminder of this valuable mineral.
Bibliography
"History of Turquoise" Americana, www.americana.net/tourq.html
"History
of Turquoise" Americana, www.americana.net/jewelry.html
"History of Turquoise" Matriq http://turquoise-amber.com/history_of_turquoise.html
Novak, Milan and Korbel, Petr, Minerals Encyclopedia, Rebo Productions,
The Netherlands 1999 p182
"ARIZONA
MINING UPDATE – for 1999"
Phillips,
K.A. , Niemuth, N.J.,
Arizona Department of Mines and Mineral Resources http://www.admmr.state.az.us/minupdat99.htm
"The mineral turquoise", The Mineral Gallery, http://mineral.galeries.com, Amethyst Galleries, Inc. 1996
"Turquoise",
The Gem Gallery www.theimage.com
"Turquoise Mineral Data", Mineralogy Database www.webmineral.com
2002
"Turquoise",
Desert USA www.desertusa.com 2003
"Lecture
16", http://ist-socrates.berkeley.edu/~esp2/wisc/Lect16.html
Perkins, Dexter
"Mineralogy: Second Edition" Prentice Hall New Saddle River,
Jersey 2002 pp472, 397
“Outline
for Earth’s Resources” Professor Johnson, Northern Kentucky
University http://www.nku.edu/~johnsonsa/Course%20Lectures/Earth%20Resources.htm
"Zuni
Pueblo" Key to Any City http://www.pe.net/~rksnow/nmcountyzunipueblo.htm
Additional Sources on Mineralogy and Turquoise Available at Earlham College Libraries
Beryllium
: mineralogy, petrology, and geochemistry / editor, Edward S. Grew.
2002.
Earlham -- Wildman Sci QD181.B4 B47 2002 c.1
Bliss,
James D. Preliminary mineral resource assessment of selected industrial
and collector minerals of the Prescott National Forest, Arizona [microform]
/ by James D. Bliss. 1999.
Earlham -- Lilly Microforms I 19.76:99-305 c.1 NonCirculating
Transformation
processes in minerals / editors, Simon A.T. Redfern & Michael A.
Carpenter. c2000.
Earlham -- Wildman Sci QE364 .T73 2000 c.1
Bishop,
A. C. (Arthur Clive) Cambridge guide to minerals, rocks, and fossils
/ A.C. Bishop, A.R. Woolley, W.R. Hamilton. c1999.
Earlham -- Wildman Sci QE363.8 .B56 1999 c.1
Hurlbut,
Cornelius Searle, 1906- Dana's minerals and how to study them : (after
Edward Salisbury Dana). c1998.
Earlham -- Wildman Sci QE365 .H845 1998 c.1
Hochleitner, Rupert. Minerals : identifying, learning about, and collecting
the most beautiful minerals and crystals / Rupert Hochleitner. [1994]
Earlham -- Wildman Sci QE373.2 .H6413 1994 c.1
MacKenzie,
W. S. A color atlas of rocks and minerals in thin section / W.S. MacKenzie,
A.E. Adams. c1994.
Earlham -- Wildman Sci QE434 .M33 1994 c.1
Dana,
Edward Salisbury, 1849-1935. Minerals, and how to study them. A book
for beginners in mineralogy. With more than 300 illustrations. 1896.
Earlham -- Wildman Sci QE365 .D16 c.1
Kaplan,
Stuart R., A guide to information sources in mining, minerals, and geosciences,
edited by Stuart R. Kaplan. [1965]
Earlham -- Wildman Reference SciRef QE26 .K3 c.1 NonCirculating
Loomis, Frederic Brewster, b. 1873. Field book of common rocks and minerals : for identifying the rocks and minerals of the United States and interpreting their origins and meanings. [1948]
Author:
Laura Norlin
Creation/revision date: April 5th, 2003
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