 There are
many different
types of 'turquoise' and sometimes what you're buying just refers to
the color. I grew up in Southern California
and 30-35 years ago, I used to travel to a few turquoise mine sources
in Nevada and the desert southwest. I don't think many mines are open
to the public these days and I still have some of that beautiful,
natural turquoise. I won't be parting with it any time soon! As a
gemologist, it's good to be able to put some of my knowledge to use!
Here is some information about the turquoise gemstone, it's origins,
treatments and characteristics that may help you when you consider
purchasing it or using the popular stone in your jewelry designs.
Most turquoise is unstable and must undergo some sort of process to
make it acceptable and durable for use in jewelry. Because it's
generally a soft and porous stone it can undergo changes in color and
texture like fading or falling apart when exposed to things such as
perspiration, sunlight, perfumes, soaps etc. Hence the need for
stabilization. A word of caution....because of its porous and fragile
nature, never tumble jewelry containing turquoise. Be sure when
oxidizing, to protect the turquoise so it does not come into contact
with any potentially damaging chemicals.
Turquoise is found in several major sources around the world, from here
in the US, (Nevada, New Mexico and Arizona and even California) China
(which does have some very beautiful gem-quality turquoise), Egypt,
Afghanistan, Iran, Africa, and Mexico. Two of the world's oldest known
turquoise mining areas are the Alimersai Mountain in Iran and the Sinai
Peninsula in Egypt.
Turquoise's lovely blue color comes from the presence of copper in the
gem material and turquoise production is often a product of copper
mining with the gemstone being a secondary mineral to the copper.
Turquoise is a hydrated phosphate of copper and aluminum and is formed
by the percolation of groundwater through aluminous rock in the
presence of copper.
I think the word "turquoise" is used pretty freely in the jewelry
world. It can be very difficult to tell just exactly what you are
buying: genuine turquoise or a pretty blue stone or compressed chaulk
that has been rolled in turquoise colored wax. I actually accidentally
bought some of this chaulk stuff one time not realizing what it was,
and while it looked nice at a glance, it was good only for coloring
paper. I think it is best when purchasing turquoise to know your
supplier.
There's nothing wrong with buying dyed howlite, reconstituted
turquoise, etc. as long as whatever you're purchasing is honestly
represented so you know exactly what you're getting. High-end turquoise
like the very beautiful robin's egg blue Sleeping Beauty variety is
very expensive. So usually, better quality equals a higher price. I
hope you can go forward with your eyes more open and with a better
understanding of what you're buying and using for your jewelry projects.
Here are some common terms and treatments. The below information was
provided by the folks at Thunderbird Supply company. I made one change
from their catalog descriptions because they had the Lab-Grown and
Synthetic descriptions reversed. The italized info is my own.
NATURAL:
Material which has not been altered in any way from how it is found in
nature. (with the exception of shaping)
ENHANCED:
A hard turquoise which is treated with varying electrical currents that
harden the stone, and enhance the color of the turquoise. No dyes,
resins, waxes or oils are used. Enhanced turquoise will not change
color over time.
STABILIZED:
Impregnated with acrylic or epoxy to harden the stone and enhance the
color. Stabilized turquoise will not change color over time.
A common method to stabilize turquoise is to impregnate the stone with
hot acrylic resins using pressure. These resins improve the hardness,
durability and color. This treatment makes is possible to use
inexpensive porous and colorless material for use in jewelry. It is
important that this material is represented as what it is.
COMPRESSED:
A treatment that uses pressure to harden the stone.
FRACTURE-SEALED:
The stone is treated with a fracture sealer which hardens the matrix in
it.
SYNTHETIC:
Artificially made substances which have all the same physical
properties and chemical composition of the naturally found substance
LAB-GROWN:
Stone produced in the laboratory, which exactly reproduces the chemical
composition and physical characteristics of the natural stone.
IMITATION:
Any compound or mineral which is manufactured to resemble the natural
product. (the 'imitation' can be stone, glass, plastic, etc.)
RECONSTITUTED
TURQUOISE:
Process of taking pieces of turquoise; chips powder or low grade, mix
with an epoxy resin, add dye, then compress into blocks. Blocks can
then be cut into different forms: beads, cabochons, carvings, flat
slabs for inlaying. Percentage of actual turquoise to resin material
varies greatly from each manufacturer. Reconstituted turquoise has a
distinctive odor due to the resin content.
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