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TURQUOISE

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Originally appearing in Volume V27, Page 483 of the 1911 Encyclopedia Britannica.
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TURQUOISE , a See also:

mineral much used as an ornamental See also:stone for the See also:sake of its See also:blue or bluish-See also:green See also:colour. It is generally held that the name indicates its source as a stone from See also:Turkey, the finest kinds having come from. See also:Persia by way of Turkey, whence it was called by the Venetians who imported it turchesa, and by the See also:French turquoise. The old See also:form turkis, used by See also:Tennyson, agrees with the See also:German Tiirkis. Some authorities have suggested that the word may be a corruption of the See also:Persian name of the stone piruzeh. Turquoise is a crypto-crystalline mineral, occurring in small reniform nodules or as an incrustation, or in thin seams and disseminated grains. Its mode of occurrence suggests its formation by deposition from See also:solution, and indeed it is sometimes found in stalactitic masses. The typical colour is a delicate See also:sky-blue, but the blue passes by every transition into green. In some cases the colour deteriorates as the stone becomes dry, and may be seriously affected by exposure to sunlight; whilst with See also:age there is often a tendency to become green, as seen in examples of See also:ancient turquoise. The mineral is always opaque in See also:mass, but generally translucent in thin splinters. Turquoise takes a See also:fair See also:polish, but the lustre is feeble, and inclines to be waxy; the hardness is nearly 6, the specific gravity between 2.6 and 2.8. Much discussion has arisen as to the chemical See also:composition of turquoise.

It is commonly regarded as a hydrous See also:

aluminium phosphate having the composition 2Al203•P205.5H2O or rather Al2HPO4(OH)4, coloured with a variable proportion of a See also:copper phosphate, or perhaps partly with an See also:iron phosphate. See also:Professor S. L. Penfield, however, has been led by careful See also:analysis of turquoise from See also:Nevada to propose the See also:general See also:formula: [Al(OH)2,Fe(OH)2,Cu(OH),H]3PO4. Hence turquoise may be regarded chemically as derived from orthophosphoric See also:acid by replacement of the See also:hydrogen by the univalent radicles Al(OH)2, &c. An ingenious counterfeit of turquoise has been formed by compressing a precipitate of cupriferous aluminium phosphate. Turquoise is usually cut as an ornamental stone in circular or elliptical form, with a See also:low See also:convex See also:surface. In the See also:East, where it is used not only for See also:personal See also:ornament but for the decoration of See also:dagger-handles, See also:horse-trappings, &c., the pieces are not unusually of irregular shape; and when worn as amulets the turquoise is often engraved with See also:Oriental See also:inscriptions, generally passages from the See also:Koran, the incised characters being gilt or inlaid with See also:gold See also:wire. The turquoise has always been associated with curious superstitions, the most See also:common being the notion that it changes colour with See also:variations in the See also:state of the owner's See also:health or even in sympathy with his affections. It is commonly held to be a " lucky stone." In Persia, where the finest turquoise is found, the mines have been worked for at least eight centuries. The workings have been described by General Houtum Schindler, an See also:Austrian, who was at one See also:time in See also:charge of the mines. The See also:principal locality is See also:north-See also:west of the See also:village of See also:Madan, on the See also:southern slopes of Mt See also:Ali-Mirsai, a See also:peak near See also:Nishapur, in the See also:province of See also:Khorasan.

Here the turquoise occurs in narrow seams in a brecciated See also:

trachyte-See also:porphyry. It is found also in some other localities in Persia and in See also:Turkestan. See also:Jean See also:Baptiste See also:Tavernier (1605–1689) states that the best turquoise, reserved for the See also:sole use of the shah, was obtained from the Vieille See also:Roche, whilst inferior stones were got from the Nouvelle Roche. These terms still survive, for turquoise of See also:fine colour is sometimes said in See also:trade to be from the " oid See also:rock," and that of See also:pale tint or of unstable See also:colours is described as from the " new rock." The latter is sometimes not true Oriental turquoise, but the material called " See also:bone-turquoise " or odontolite, and known also as " occidental turquoise." This is merely fossil bone or See also:ivory coloured by iron phosphate (See also:vivianite) or perhaps stained in some cases by cupriferous solutions, and is readily distinguished from true turquoise by showing organic structure under the See also:microscope. Bone-turquoise occurs in See also:Europe; and it may be noted that mineral turquoise also is known from certain localities in See also:Saxony and See also:Silesia, but the quantity is very limited and the quality poor, so that it has no commercial importance. See also:Chrysocolla has been sometimes mistaken in various parts of the See also:world for turquoise. In 1849 turquoise was found by See also:Major C. See also:Macdonald in See also:Wadi Maghara and Wadi Sidreh in the Sinaitic See also:Peninsula; and a large See also:series of the specimens was shown in the See also:Great See also:Exhibition of 1851. According to H. Bauerman, who described the locality geologically, the turquoise occurs in a red See also:sandstone, in the form of embedded nodules and as an incrustation lining the See also:joint-faces. The turquoise was worked for some time by Macdonald, and many years afterwards workings were resumed on a systematic See also:scale by an See also:English See also:company, but without great success. See also:Relics of extensive ancient See also:mining operations for turquoise show that the rock was at one time worked with See also:flint implements.

The locality was examined by Professor See also:

Flinders See also:Petrie in 1905. In ancient See also:Mexico much use was made of turquoise as an inlay for See also:mosaic See also:work, with See also:obsidian, See also:malachite, See also:shell and iron See also:pyrites. Such work is illustrated by fine specimens in the ethnographical See also:gallery of the See also:British Museum and elsewhere. Relics of extensive workings are found in the mountains of Los Cerillos near See also:Santa Fe in New Mexico, where mining for turquoise is now actively carried on. One of the hills in which old workings occur has been called Mt Chalchihuitl, since it is believed that the turquoise was known by the name chalchihuitl, which in some places was applied also to See also:jade. Another of the Cerillos hills in which workings have been opened up is called Turquoise See also:Hill. The See also:matrix at Los Cerillos is described by D. W. See also:Johnson as an altered angite-See also:andesite, in which the turquoise occurs in thin See also:veins and in small nodules in patches of See also:kaolin. It appears probable that the alumina of the turquoise was derived from the alteration of See also:felspar, and the See also:phosphorus from See also:apatite in the rock, whilst the copper was brought up by heated vapours which altered the andesite. Turquoise is found also at Turquoise See also:Mountain, Cochise See also:county, See also:Arizona, and at Mineral See also:Park, See also:Mohave county, in the same state ; it occurs in the See also:Columbus See also:district, southern Nevada; in See also:Fresno county, See also:California; and near See also:Idaho, See also:Clay county, See also:Alabama. Mexican turquoise is known from the state of See also:Zacatecas.

Turquoise was discovered in 1894 near Bodalla, in New See also:

South See also:Wales; and it has also been found in See also:Victoria. Turquoise is sometimes termed by mineralogists callaite, since it is believed to be the callais of See also:Pliny—a stone which he describes as resembling lapis lazuli, but paler, and in colour more like the shallow See also:sea. The callaina of Pliny was a pale green stone from beyond See also:India, whilst his callaica was a See also:kind of turbid callaina. The name callainite was suggested by Professor J. D. See also:Dana for a See also:bright green mineral which was found in the form of beads, with stone hatchets, in ancient See also:graves near Mane-er-H'roek (Rock of the See also:Fairy), near See also:Locmariaquer in See also:Brittany, and which A. Damour sought to identify with Pliny's callais. The mineral in question seems to be identical with See also:variscite, a hydrous aluminium phosphate named by A. Breithaupt, and occurring as a beautiful green amorphous mineral, sometimes polished as an ornamental stone; fine examples occur in See also:Utah. Somewhat allied to turquoise is the blue mineral called lazulite (to be distinguished from lazurite, see LAPIS LAZULI), which has the formula (Fe2Mg)Alz(OH)(PO4), and has occasionally been used as an ornamental stone. (F. W.

End of Article: TURQUOISE

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