' TURQUOTS. 



■n-ithout alteration : for this quality it is 

 much esteemed, although in other respects 

 not so good as the produce of Ansar.'' Now, 

 the Calaite, which contains 18 per cent, of 

 water, would be entirely destroyed by such 

 an operation, while the Bone Turquois is 

 actually made in many places by exposure 

 to the fire of fossil bones impregnated with 

 iron ; and the fossil bones brought from the 

 north of the Himalayan range, when ex- 

 posed to a red heat, are found to assume 

 the very appearance of Odonto/ite ; it is 

 possible, therefore, that a supply of this 

 artificial gem may find its way into Persia 

 through Balkh, and take its name from that 

 country as its known market. Arguments 

 on the other hand to show that the Badak' 

 shdyii Turquois is nothing more than Lapis 

 Lazuli, or lajaward, and the descriptions of 

 the two are mixed up together like those of 

 the Emerald and Topaz." 



As stated above, the best stones are ob- 

 tained from Persia ; but the largest and 

 most beautifully tinted specimens rarely 

 reach Europe, being retained by the Shah 

 for his own use, or bought up by the 

 grandees of that and the adjoining Maho- 

 metan states. An inferior Turquois (^Firozeh 

 nakis) is enumerated amongst the mineral 

 products of Thibet. Less pure varieties are 

 found in Silesia and Oelsnitz, in Saxony. 



The Turquois cut in low cabochon is 

 much employed in jewelry, on account of 

 its beautiful tone of colour, which contrasts 

 agreeably with diamonds, pearls and gold, 

 and is not impaired by candlelight. It is 

 frequently imitated, and with much sviccess, 

 so far as colour is concerned ; but the arti- 

 ficial stone may be readily distinguished 

 from the real by its greater vitreous lustre 

 and gloss. In the real stone there are, 

 generally, moreover, minute conchoidal frac- 

 tures round the girdle, where it has been 

 left rough, in order to receive the setting, 

 which afford a certain mark of distinction. 

 Turquois de nouvelle roche (Odontolite; 

 is found in Bas Languedoc. The Tur- 

 quois is frequently engraved in intaglio by 

 the people of the East, and the hollows 

 covered with gold, presenting to the eye 

 a kind of damascening. It was also en- 

 graved by the Greeks and Romans, but, 

 mostly in relief. Numbers of Turquois 

 rings are still in existence with the phallus 

 (which is believed to have been the dis- 

 tinguishing emblem of the Roman cavaliers) 

 engraved in relief upon them. 



Brit. Mus., Case 57. 



3L P. G. Horse-shoe Case, Nos. ,1 ^26 to 



in2. 



TYRITE. 391 



In the Horse-shoe Case at the Museum of 

 Practical Geology, there is a very fine col- 

 lection of Turquoises, which obtained the 

 prize medal at the Great Exhibition of 1851. 

 (See Nos. 1126, 1127.) 



They were brought by Major C. Mac- 

 donald from Arabia Petrea, from five or six 

 localities, all included within arange of about 

 forty miles, in the country of Sonalby, six- 

 teen daj's' journey 8.E. of Suez. Most of 

 the specimens were found in the ravines on 

 the further side of a chain of mountains hav- 

 ing an east and west direction, and a mean 

 elevation of five or six thousand feet : but 

 some were met with in situ. These latter 

 are still attached to the parent rock, which 

 is a reddish sandstone composed of Quartz 

 grains, and resembling in appearance the 

 Old Red Sandstone of Brecon. 



" The colour of the turquoises discovered 

 by Major Macdonald, ditfers in, the shade of 

 blue from that of the turquoises of Persia, 

 but agrees exactly with those brought from 

 Abyssinia by M. Rochet d'He'ricourt. Both 

 exhibit small globular concretions, Avhose 

 hardness is equal to that of agate. The 

 nodules of turquoise form groups almost 

 like currant-seeds in the sandstone. The 

 intensity of the colour of adjacent lumps is 

 different ; and when the groups are of 

 tolerably large dimensions, zones of diff"erent 

 tints may be observed. 



" This'collection also, presents, besides the 

 small concretions, veins of turquoise from a 

 tenth to a twentieth of an inch thick, Avhich 

 cut across the bedding of the sandstone like 

 small threads." — Reports of the Juries. 



Tyrite, David Forbes. A mineral allied 

 to, and perhaps identical with, Fergusonite. 

 Colour varying from greyish-brown to rich 

 clove-brown. Lustre resinous to semi- 

 metallic. Translucent in thin splinters. 

 Streak yellowish-brown. Brittle. Fracture 

 splintery and conchoidal. H. 6*5. S.G. 5-i3 

 to 5-36. 



nahjsis, by David Forbes : 





Columbic acid 



. 44-48 



Yttria .... 



. 27-83 



Alumina 



. 3-65 



Protoxide of cerium . 



. 6-63 



Protoxide of uranium . 



. 5-99 



Protoxide of lanthanium 



. 1-47 



Protoxide of iron . 



. 2-11 



Lime .... 



. 1-68 



Zirconia (and glucina.') 



. 2-78 



Binoxide of tin . 



. trace 



Water .... 



. 4-66 



100-18 



