The turquois is never found in crystals, but in reniform or stalactitic masses. The color varies from pea- and apple-green to greenish-blue, sky-blue and dark-blue.
The hardness of the turquois is 6., specific gravity 2.6 to 2.8, lustre waxy, and condition opaque to slightly translucent.
Before the reducing flame of the blow-pipe, the turquois does not melt, but becomes brown and colors the flame green. With borax and salts of phosphorus the turquois melts to a clear glass, while it is also soluble in hydrochloric acid. Oriental or mineral turquois is composed of:
| Alumina | 47.45 |
| Phosphoric acid | 27.34 |
| Water | 18.18 |
| Oxide of copper | 2.02 |
| Iron | 1.10 |
| Oxide of manganese | 0.50 |
| Phosphate of lime | 3.41 |
| 100.00 |
The best color is a clear deep sky-blue, and in the true turquois this color improves by artificial light; imitation turquoises, however, lose their fine color under the same conditions.
The finest gem turquoises come from the northeastern part of Persia, between Nishapoor and Meshed. Here they are mined and partly cut, and then the Persian merchants carry them to Russia, where they are sold at the great annual fair of Nijni-Novgorod and in Moscow. Mineral turquoises are also found in New Mexico, Arizona, and Nevada, but not of sufficient size or sufficiently good color to make gem stones, although they are prized for collections. Specimens are also found in Burmah, Khorassan, Thibet, China, Silesia, Saxony, and on the Isthmus of Suez. The stones from these places have, as a rule, but little value, as the color fades or turns green from exposure to the light. Of late however, some very good turquoises have come from Egypt. The color of a faded Persian turquois can sometimes be restored by simply repolishing the stone.
Occidental or bone turquoises called new rock or odontolites, to distinguish them from the Persian or old rock stones, are of organic origin.
They are cut from the teeth of mammoths, mastodons, dinotheriums, etc., and are found near the town of Simor, in Lower Languedoc, France.
These teeth, the enamel of which is nearly as hard as the mineral turquois, are colored by contact with phosphate of iron and copper, which gives them a dark-blue, light-blue, and bluish-green color. They are easily attacked by a file, and totally destroyed by aqua-fortis.
When heated, the fossil turquois or odontolite gives an offensive odor, owing to the decomposition of animal matter.