| Turquoise has been of great interest to even prehistoric man. In the Western hemisphere in the burial sites of prehistoric peoples the stone was found in abundance.
The Anasazi and Hohokam mined turquoise throughout the Southwest. Turquoise is known to be a popular trade item because it was found hundreds of miles away from the mining sites of New Mexico in Mexico with the Aztecs.
It seems that turquoise was considered a stone of life and good fortune and had healing properties. In Egypt, the earliest known use of turquoise and the first mines of Sinai, it was mentioned as having mystical powers and was used in the art figures and ornaments.
In India it was used in art, medicine, and jewelry. In Tibet every Tibetan carried or wore a piece of turquoise all their life. In North and South America the stone was used in religion, art, trade, treaty negotiations as well as for jewelry. It was considered to be associated with life itself.
It was thought to prevent injury through accident, prevent blindness, by placing on the eyes or ground into a slave and as a powder. It was ingested to cure stomach disorders, internal bleeding, and stings from snakes and scorpions.
Their colors could forcast the good or bad, predict the weather and influence dreams. It was good for almost any ailment including insanity.
Turquoise consists of the chemical elements copper, aluminum, phosphorus, hydrogen and oxygen in the form of water.
Most turquoise is found in ‘alteration zones’ where the native original rocks have been altered thru the intrusion of other rocks from some volcanic or other thermal influence.
The color of turquoise can vary from deep blue to deep green with every variation in between. Generally the more copper in the molecule, the bluer the turquoise. Iron in the stone makes it greener. More moisture will also cause turquoise to turn greener in color.
Placing turquoise in animal fat can change the stone to a deeper color. Dipping it in water can also alter the color. These methods are only temporary though.
There are 4 types of turquoise you will see in the jewelry market
- Natural - This comes directly from the mine. It is cut shaped and polished and set into jewelry. It has no man made treatment or additives other than a polishing compound that adds to its luster. Most stones in this state are very close to gem quality.
- Stabilized – This is a natural turquoise usually in nugget form, but does not hold a luster. It is submerged into a stabilizing compound and dried, cut and prepared for jewelry. The turquoise has not been altered. The pores of the stone have been filled with a clear resin that makes the stone usable. This process allows for diversity of shapes and possibilities in jewelry making. Color Stabilized stones ARE altered and the color has been added by this process. This in not necessarily bad, but it has less value than a piece that is naturally colored.
- Treated - This form of color enhancement has been used for thousands of years. It is done as discussed earlier by submerging into animal fat or vegetable oil and later air dried. This will not last very long.
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Fake and Synthetic – Ceramics, bone, celluloid and plastic are used to imitate turquoise. Synthetic turquoise has a very natural matrix that is produced by placing stones in the synthetic “batter”
Hardness / Density. This is a critical factor in determining the grade of a turquoise specimen. An inferior, chalk-like turquoise will feel light; it will be porous and stick to your tongue. The harder, denser pieces will have a “good” substantive feel to them. They will not draw the same quantity of moisture from your tongue as lower grades, but you will feel some adhesion to your tongue. As density increases, so too does hardness. Just as turquoise varies from a little over 2 to nearly 6 on the Mohs scale, its specific gravity also varies but typically is 2.8, like quartz.
Color. No area is less codified than this. The ancients preferred blue because a gem-grade blue stone would not change color (King Tut’s treasures include a substantial amount of blue turquoise — it appears today unchanged). Because the softer blue stones would eventually start turning greenish, it was assumed that green was not as good. Time has proven this wrong. Some green-hued turquoise such as Skyhorse, China Mountain (both are names given to turquoise from China), Cerillos, Blue Gem, and Fox, to name a few, are ranked in the top three grades, like blue stones from the Lander, Lone Mountain, Red Mountain, Morenci, and Bisbee mines. To make matters even more difficult, some mining areas — such as Skyhorse, China Mountain, Blue Gem, and Royston — produce both colors.
Matrix. This is the host rock in which the turquoise forms and bonds. When cut, the host rock and the turquoise are one piece. The pattern of this matrix must be pleasing. This is subjective at best, but with experience, you learn what most people consider most desirable. Again, as in color, the opinions on which matrix is “best” varies dramatically. There are hard-core supporters of the fine, dark, spider web found in the Lander, Number Eight, Lone Mountain, Red Mountain, Skyhorse, and China Mountain mines. The heavy brown-black matrix of Bisbee and Tyrone has followers who believe it is the world’s best. A hard, lustrous cabochon from Morenci typifies another beautiful and highly regarded matrix. It is freeform, with a blending of webbing and deep pattern matrix combined with visible pyrite inclusions.
Turquoise is considered a precious stone. At one time in history, superior specimens were valued by weight, more than gold. Today, turquoise ranges from a few cents per carat (chalk) to over $100 per carat for a superb gem stone. It is widely regarded as our nation’s “national stone.” Man has coveted, romanced, fought for, and owned this remarkable stone with pride.
to read more about turquoise please go to your local library or go to www.americana.net |
