Turquoise

Written by Administrator

Tuesday, 13 November 2007

Turquoise The turquoise has remained almost unrivaled in its popularity throughout the centuries. Five thousand years ago the Egyptians mined these attractive blue and green stones in the Sinai Peninsula and then set them in varied mosaics and jewelry. Although these ancient mines are still partially worked today, the principal source of the finest deep-blue stones is in the Khorasan province of Iran. Chemically, turquoise is a complex phosphate of aluminum with a hard¬ness of 6 on the Mohs scale. Its blue color, which makes it so attractive, is due to the presence of a copper compound. Small individual crystals are extremely rare, some having been found in the United States, but the bulk of this mineral is found in masses composed of innumerable tiny crystal grains. It is thus cryptocrystalline in composition. In earlier days, faultless stones of a single blue color were most valued, but today, because pure turquoise is almost unavailable, the so-called tur¬quoise matrix, which is turquoise interspersed with dark veins of limonite, is popular. Because of its porosity, turquoise is sensitive to chemicals and should not be brought into contact with soaps and detergents. The color of some stones may fade if exposed to light for a long time, while specimens of a fine blue color may turn green. Fossil bones and teeth of prehistoric animals colored blue or green by iron phosphate are occasionally unearthed. These fossil remains are known as odontolite, or bone turquoise, but their organic structure can easily be detected with a strong lens or by the use of a microscope.

Last Updated ( Tuesday, 13 November 2007 )