7 Mayıs 2013 Salı

New Mexico State Gemstone

New Mexico State Gemstone


Turquoise is an opaque mineral, a hydrated phosphate of copper and aluminum. It is also formed by the percolating action of meteoric waters, usually in arid regions or deserts, on aluminous igneous or sedimentary rocks.
Turquoise comes in various shades of blue, blue-green, green-blue, green, yellow-green, and yellow. The material can be solid colored or spider-webbed in any of these different colors or shades. The quality varies from hard, solid material that takes a good polish, to soft porous material that can only be used as feed stock for treatment, enhancement, or stabilization processes.
Turquoise is closely associated with the southwestern United States, and especially with New Mexico. That state’s production of turquoise from deposits in the Cerrillos Hills, Santa Fe County; the Burro Mountains and Little Hachita Mountains, Grant County; the Jarilla Hills, Otero County; and the Guadalupe Mountains, Eddy County can be traced to prehistoric Amerindian cultures. Several different mines operate or have operated at each of these locations, producing seam and nugget turquoise.
Many of the more famous and higher-quality deposits are economically depleted. Turquoise from these New Mexican deposits was as good as from any deposit in the world and was the first to displace true Persian turquoise in the U.S. market. The New Mexico State Legislature adopted turquoise as the official state gemstone on March 23, 1967.
Arizona designated turquoise its state gemstone in 1974. Nevada designated turquoise its state semiprecious gemstone in 1987.
The name turquoise is antiquated French for "Turkish," because at one time, turquoise came to France from Turkey. The stone was apparently also referred to as "turquin," another old term meaning "Turk." However, the turquoise in question most likely originated in Alimersai Mountain in Persia (now Iran) or the Sinai Peninsula in Egypt, two of the world's oldest known turquoise mining areas. The unique color of the stone has led to its use to describe anything similarly colored.
Geographic Distribution
Turquoise was one of the first minerals to be mined, and continues to be mined mostly by hand. Egyptians mined and used turquoise from the Sinai Peninsula about 3,000 years ago, and six mines remain in the region.
An area near Neyshabur, Iran, has been mined for over 2,000 years and continues to supply some of the world’s finest turquoise. For thousands of years, the finest intense blue turquoise in the world was found in Persia, and the term "Persian turquoise" became synonymous with the finest quality. This changed during the late 1800s and early 1900s when modern miners discovered or rediscovered significant deposits of high-quality turquoise in the western and southwestern United States. Material from many of these deposits was just as fine as the finest Persian turquoise. Today, Persian turquoise more often describes the stone’s quality than its origin, and the majority of the world’s finest-quality turquoise comes from the United States, the largest producer of turquoise.
Until the 1920s, New Mexico was the United States’ largest producer of turquoise. Currently, with the exception of byproduct material from copper mines, production of turquoise from deposits in New Mexico, for all practical purposes, has stopped. Turquoise still can be found in New Mexico, but Arizona and Nevada have surpassed it in terms of both annual and total production.
Turquoise is one of the oldest gemstones known. Pharoahs, Aztec kings, and the people of Persia, Mesopotamia, and the Indus Valley civilization adorned themselves with turquoise jewelry.
Since about 200 BCE, turquoise has been extensively used by both southwestern U.S. Native Americans and by many indigenous tribes in Mexico. The popular Native American jewelry with turquoise mounted in silver is relatively new. Some believe this style of jewelry was unknown prior to about 1880, when a white trader persuaded a Navajo craftsman to make turquoise and silver jewelry using coin silver. Prior to this time, Native Americans made solid turquoise beads, carvings, and inlaid mosaics.
China and Tibet are minor sources of the mineral. Sacred to Tibetans, turquoise is often used by shamans in rituals and ceremonies. It is believed to promote mental and spiritual clarity and expansion, as well as enhance wisdom, kindness, trust, and understanding.
Turquoise is the astrological birthstone for Taurus and Sagittarius, the planetary stone for Aquarius, and one of four modern birthstones for December. It is also the Russian and Polish birthstone for December, and the fifth and 11th wedding anniversary stone. It is one of the most valuable nontransparent minerals used in jewelry.
Egyptians were the first to produce artificial turquoise, which was used in glazed earthenware. The most common imitation of turquoise encountered today is dyed howlite and magnesite, both white in their natural states. Howlite also has the natural (and convincing) advantage of black veining similar to that of turquoise. Dyed chalcedony, jasper, and marble are less common, and much less convincing.
Two other gem materials that can resemble certain colors and shades of turquoise but are separate mineral species are variscite and faustite. Both have been mistaken for and marketed as turquoise. Attractive gemstones can be cut from both variscite and faustite, and therefore would be noteworthy as gem materials on their own.
State GemstoneTurquoise Gem Rough
State Gemstone
Polished SpecimenState Gemstone
Turquoise Chips
State Gemstone
Finished Pendant
Group: Turquoise 
Chemical Formula: CuAl6(PO4)4(OH)(H2O)
Crystal Structure: Triclinic
Hardness (Mohs): 5-6
Color: bright blue, sky-blue, pale green, blue-green, turquoise-blue, apple-green, green-gray
Transparency: Opaque
Luster: Vitreous, waxy, dull
Birefringence: +0.040
Pleochroism: Weak
Refractive Index: ná = 1.610 nâ = 1.615 nã = 1.650
Density: 2.6 - 2.8 g/cm3
Streak: Pale greenish blue to white
Cleavage: Perfect
on {001}, good on {010}
Fracture: Conchoidal

Some data courtesy of the Mineralogical Society of America
Author: World Trade Press

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