It is thought that the word turquoise comes from the fact that Levantine traders, commonly known as Turks, brought the material to Europe from their homes in the Eastern Mediterranean by. We find references to turquoise ornaments as far back as with the Egyptians, thousands of years ago (4000 - 5000 B.C.E.) and then a millennium later in Mesoamerica and China. The Aztecs mined turquoise in what is now New Mexico. The Victorians also greatly admired turquoise, and generally set it in gold.
The first turquoise of jewelry quality came from Iran, formerly Persia. Today, turquoise mined in the south west of United States rivals that of Iran and the term "Persian Turquoise" now refers to turquoise has no black or brown veining. Turquoise mined in the United States and used in jewelry created by the American Indians, has that characteristic veining (an even, interconnected patterning of black matrix veins). Stones of this type are referred to a "spiderweb" turquoise.
Some turquoise also comes from Arizona, California and Nevada in the United States. To many Native Americans, the stone is sacred and was carved into symbolic animals and birds. We can find turquoise carvings Indians tombs, because the Indians believed that the stone would attract good spirits who would stand guard on the dead. We also know that Medicine Men used the stone in healing ceremonies and warriors attached turquoise to the end of their bows, in an effort to help the accuracy of their bow shots.
Minerals like chrysocolla are used to make fake turquoise. Sometimes, turquoise is dyed and stabilized with resins to produce a harder stone that keep its color and polish. It's been found that plastic impregnation, sometimes with dye, improves durability and color. Reconstituted turquoise can be made from chips and "chalk." Dyes and plastic resins are added. Very few pieces of turquoise can, without enhancements, be highly polished, so most turquoise has been enhanced. Even high quality stones have their surfaces coated with paraffin wax, which seals them and enhances their polish.
Turquoise is relatively fragile, porous, and susceptible to heat and/or chemical damage, because it has about a 20% water content. When the gem is heated, water is lost. At 400 degrees Centigrade, the structural integrity of the mineral is destroyed.
The color of turquoise ranges from green and greenish blue to sky blue shades. It is soft stone that is between a five and a six on the Mohs scale of hardness. Because of its properties, turquoise rings and bracelets should not be worn as "everyday" items and it should be kept away from heat, chemicals and shocks. Skin oils and cosmetic residues may change and darken the color of turquoise gems. That means hand cleaning only, no ultrasonic or steam cleaning. It's best to just wash turquoise jewelry with a soft brush in mild, lukewarm, soapy water. After each wearing, pieces should be wiped with a damp cloth.