The name of the species comes from a French word meaning Turkish, and arises from the fact that the gem-stone first reached Europe by way of Turkey. Another, but less obvious, suggestion is that it is derived from the Persian name for the species, _piruzeh_. Our turquoise and other phosphates of similar appearance were probably known to Pliny under the three names _callais_, _callaina_, and _callaica_. The finest turquoise still comes from the famous mines near Nishapur in the Persian province of Khorassan, where it was known in very ancient times; it is found with limonite filling the cracks and cavities in a brecciated porphyritic trachyte. Pieces of the turquoise and limonite from here are sometimes cut without removal of the latter, and sold as ‘turquoise-matrix,’ when the precious stones are too tiny to be worth separate working. It also occurs at Serbâl in the Sinai Peninsula. Among the more recent localities may be mentioned Los Cerillos Mountains, New Mexico; Sierra Nevada, Nevada, where pale blue and green stones are found; San Bernardino County, California, where again the stones are rather pale; and Arizona, where it occurs in pale greenish-blue stones. Some of the stones that have been seen are not the true turquoise but odontolite, or bone turquoise, which consists of the teeth and bones of mastodon or other extinct animals, phosphate of iron being the colouring material. These stones may easily be recognized by their organic structure, which is clearly visible if viewed with a strong lens or under the microscope. Moreover, odontolite invariably contains some calcium carbonate, and effervescence takes place if it be touched with hydrochloric acid. Turquoise dissolves in hydrochloric acid, but without effervescence, and since it contains copper, a fine blue colour is imparted to the solution by the addition of ammonia. Odontolite has a higher specific gravity, 3·0 to 3·5, but lower hardness, 5 on Mohs’s scale. Variscite, the hydrated phosphate of aluminium, corresponding to the formula AlPO_{4} + 2H_{2}O, is found in masses resembling a greenish turquoise, but it is much softer, being only 4 on Mohs’s scale. The specific gravity is 2·55. Round nodular masses of variscite are found in Utah. CHAPTER XXXIII JADE