Turquoise

Turquoise
Name	Turquoise
Caption	A turquoise specimen from Nishapur, Iran
Category	Phosphate mineral
Formula	CuAl8(PO4)6(OH)8·4H2O
Crystal system	Triclinic
Cleavage	None
Mohs scale	5-6
Luster	Waxy to subvitreous
Streak	Blue-green
Density	2.9-3.3
Optical properties	Biaxial (-)
Refractive index	1.61-1.65
Dispersion	0.016

Turquoise is a copper aluminum phosphate mineral, often found in Iran, Egypt, China, and the Southwestern United States. It has been highly valued for its vibrant blue-green color, which is reminiscent of the Mediterranean Sea and the Caribbean Sea. Turquoise has been used in jewelry and decorative objects by various cultures, including the Ancient Egyptians, Aztecs, and Native Americans, such as the Navajo Nation and the Zuni people. The mineral is also associated with the Tiffany & Co. jewelry company, which has used it in many of its designs, including those created by Jean Schlumberger and Elsa Peretti.

Introduction

Turquoise is a relatively rare mineral, often found in arid regions such as the Gobi Desert and the Mojave Desert. It is typically associated with copper deposits, and its formation is often linked to the weathering of copper ore. The mineral has been used for centuries in various applications, including jewelry, decorative objects, and even as a pigment in art. Turquoise is also the official state mineral of New Mexico, where it is found in significant quantities, particularly in the Cerrillos Hills and the Santa Fe National Forest. The New Mexico Museum of Natural History and Science has an extensive collection of turquoise specimens, including those from the Laguna Pueblo and the Acoma Pueblo.

History

The history of turquoise dates back to Ancient Egypt, where it was used in jewelry and decorative objects, such as the Mask of Tutankhamun and the Tomb of Nefertari. The mineral was also highly valued by the Aztecs and the Mayans, who used it in their ceremonial objects, such as the Calendar Stone and the Pyramid of the Sun. In the United States, turquoise was used by Native Americans, such as the Navajo Nation and the Zuni people, in their traditional jewelry and decorative objects, including kachina dolls and woven baskets. The Spanish conquest of the Aztec Empire and the Mexican-American War also played a significant role in the history of turquoise, as the mineral was often used as a form of currency and trade, particularly in the Santa Fe Trail and the California Trail.

Geology

Turquoise is a secondary mineral, often formed through the weathering of copper ore. It is typically found in arid regions, where the oxidation of copper is more likely to occur, such as in the Atacama Desert and the Australian Outback. The mineral is often associated with other copper minerals, such as malachite and azurite, and is typically found in veins or nodules, particularly in the Copper Mountain and the Sierra Nevada. Turquoise is also found in sedimentary rocks, such as limestone and sandstone, particularly in the Grand Canyon and the Zion National Park. The United States Geological Survey (USGS) has conducted extensive research on the geology of turquoise, particularly in the Southwestern United States, where it is found in significant quantities, including in the Turquoise Trail and the Cerrillos Hills.

Properties

Turquoise is a relatively soft mineral, with a Mohs hardness of 5-6, which is similar to that of apatite and scapolite. It has a waxy to subvitreous luster, and its streak is typically blue-green, which is reminiscent of the Mediterranean Sea and the Caribbean Sea. The mineral is also biaxial, with a refractive index of 1.61-1.65, which is similar to that of quartz and feldspar. Turquoise is often porous and may contain inclusions, such as pyrite and calcite, particularly in the Nishapur and Egyptian varieties. The American Gem Trade Association (AGTA) has established standards for the grading and classification of turquoise, particularly in the United States, where it is highly valued for its vibrant blue-green color, including in the Tiffany & Co. jewelry company.

Cultural_Significance

Turquoise has significant cultural and historical importance, particularly in the Southwestern United States, where it is highly valued by Native Americans, such as the Navajo Nation and the Zuni people. The mineral is often used in traditional jewelry and decorative objects, such as kachina dolls and woven baskets, particularly in the Santa Fe Indian Market and the Gallup Intertribal Ceremonial. Turquoise is also associated with the Tiffany & Co. jewelry company, which has used it in many of its designs, including those created by Jean Schlumberger and Elsa Peretti. The Smithsonian Institution has an extensive collection of turquoise specimens and artifacts, including those from the Laguna Pueblo and the Acoma Pueblo, which are on display at the National Museum of Natural History and the National Museum of the American Indian.

Mining_and_Trade

Turquoise is mined in several countries, including Iran, Egypt, China, and the United States. The mineral is often extracted from open-pit mines or underground mines, particularly in the Nishapur and Cerrillos Hills regions. The global trade of turquoise is significant, with the mineral being highly valued for its vibrant blue-green color, particularly in the jewelry industry, where it is used by companies such as Tiffany & Co. and Cartier. The International Colored Gemstone Association (ICA) has established standards for the grading and classification of turquoise, particularly in the global market, where it is highly prized for its beauty and rarity, including in the Hong Kong and Dubai markets. The United States Customs and Border Protection (CBP) also regulates the import and export of turquoise, particularly in the Southwestern United States, where it is highly valued by Native Americans and jewelry collectors.

Category:Minerals