CATALOGUE OF OEMS. 535 



color is liuhle to c-liungo, :i tine ])lue stone becoming a verdigris or 

 sickl\' green. 



Tur(|iioise of poor color is frequently given the approved robin's-egg 

 or peculiar bluish green tint by artiticial means. Many of these 

 sophistications can be detected by washing the stone in strong ammo- 

 nia water, which will attack the coloring matter. The reagent does not 

 iitl'ectjJie color of the true Persian tunpioise, although soap and water 

 ^JiJP^ so that the hands should never be washed with a turquoise on 

 them. 



The ])est specimens, which generally do not lose their color easily, 

 come from the vicinit}'^ of Nishjipur, Persia, where they occur in nar- 

 row seams and irregular patches in the brecciated portions of a por- 

 phvritic trachyte and the surrounding clay slate. Inferior specimens 

 art> found in Asia ]Minor, Turkestan, and the Kirghiz Steppes. In the 

 United States, turquoise is found in a trachytic rock in the Los Ceril- 

 los Mountains, near Santa Fe; the localit}' was early worked by the 

 Indians and has lately afforded some fine gems. Other occurrences 

 are at Turquoise Mountain, Cochise County, and Mineral Park, ]Mojave 

 County, Arizona; near Columbus, Nevada; at the Holy Cross Moun- 

 tain. Colorado, and in Fresno and San Bernardino counties, California. 



Chemical!}', the turquoise is a hydrous phosphate of aluminum and 

 copper and contains in 100 parts: Phosphoric acid, 30.9; alumina, 

 •1:4.50; oxide of copper, 3.75; water, 19. 



VARISCITE. 



The compact massive kinds of variscite are occasionally cut for use 

 as a gem. The color of the mineral is a rich green of several shades, 

 bright green, emerald, and bluish green. Hardness, 4; specific gravity, 

 2.6. It takes a high polish, and its strong rich colors would make it 

 an attractive ornamental stone were it not so soft. The best variscite 

 is found in compact nodular masses, locall}' called ntahlte^ near Lewis- 

 ton, Cedar Valley, Tooele County, Utah. 



Variscite contains in 100 parts: Phosphorous pentoxide, 41.9; alum- 

 ina, 32.3; water 22.8. 



VESUVIANITE. 



CYPRIXE — IDOCRASE. 



Vesuvianite occurs in tetragonal crvstals conunoidy of a prismatic 

 habit and massive, either columnar or granular. Hardness, 6.5; 

 specific gravity, 3.349 to 3.45, Luster, vitreous, often inclining to 

 resinous. Color, brown to green, the latter frequently ])right and 

 clear and appearing of a different color when viewed across the lateral 

 axis of the prism; occasionally sulphur-yellow, wine-yellow, pale blue, 

 and black. 



NAT MUS 1900- 37 



