Turquoise is a blue-green mineral, a copper aluminum phosphate, valued for its rarity and unique hue, and widely used as an ornamental stone. Popular in the 16th century to adorn places of worship in Turkey, it was eventually traded in Turkish bazaars and brought to Europe by merchants and travelers. This stone is fragile — just slightly stronger than window glass — so special care must be taken during extraction and transport.
The bluer the stone is, the more expensive. Variations in color are due to the presence of metals, such as iron impurities in the case of green turquoise. Most original mines were depleted a long time ago, and the current supply comes mostly as a byproduct of copper mining. Iran is the world's largest producer of this mineral; it is also mined in the Southwest US, primarily in Arizona and Nevada. This has made the stone a popular choice to create Native American jewelry and religious tiling and decoration.
In the past, the mineral was worn only by rulers, especially by Ancient Egyptian pharaohs, Aztecs kings, and Chinese emperors. Often set in gold and combined with other stones such as jade, quartz, and malachite, it was thought to be a magical stone that could protect the wearer from malignant forces. Apache and Navajo tribes also considered the stone a powerful amulet, although everybody was allowed to wear it.
It is now possible for this mineral to be bought and used by anybody, provided they can afford it. If price is a consideration, artificial turquoise is available. While early imitations were made of glass and enamel and easily identifiable, new versions are not distinguishable to the untrained eye.
Turquoise needs to be cared for to stay in top condition. The stone is sensitive to chemicals and naturally fragile, so it should not come in contact with strong perfumes or cleaning chemicals, should be kept away from direct sunlight, and should not be hit or knocked against hard surfaces. It is easily scratched, so owners must care for it during storage as well. The mineral also needs to "breathe" to conserve its deep natural color. Lack of air will eventually turn the stone greenish, contributing to it losing its value.