COLUMBATES, PHOSPHATES, VANADATES 519 



r.mdmi.lal; H. = 6; G. = 2.6-2.86; Color, sky-blue to apple- 

 ureen ; Streak, white to pale green; Luster, waxy; Subtranslucent 

 ti opaque; a = 1.61, V = 1.65, y a = .04. 



B.B. Infusible, becoming brown and glassy, yields a green 

 flame. The S. Ph. bead reduced with tin shows copper. In the 

 dosed tube yields water. 



General description. Crystals of Turquoise were discovered for 

 the first time at Lynch Station, Campbell County, Virginia, and de- 

 srribed within the year. They were very small and scarce. Usually 

 occurs in amorphous masses filling small veins in altered porphy- 

 ries. In the United States turquoise is mined extensively at 

 Mineral Park, Mohave County, Arizona; Washoe County, Ne- 

 vada ; Burro Mountains, New Mexico. 



The blue color is due to copper, and in many specimens fades on 

 exposure. The finest gem turquoise is found near Mishapur, 

 Persia. Turquoise has been used as a gem from remote ages, as 

 the bracelets discovered at El Mehesna, the oldest known jewels, 

 contained beads of turquoise alternated with beads of gold. 



The American material is slightly soft and porous, which affects 

 the polish. 



Variscite. A1PO 4 . 2 H 2 ; a crystalline hydrous phosphate of 

 aluminium, very similar to turquoise in color, but lighter green to 

 deep emerald green. It contains no copper and occurs in south- 

 western Utah, where it is found as nodules contained in a lime- 

 stone, associated with jade, chalcedony, and limonite. 



TORBERNITE 



Torbernite. Hydrous uranyl phosphate of copper, Cu(U0 2 ) 2 - 

 (P0 4 ) 2 . 8 H 2 0; Cu = 8.4, UO 3 = 61.2, P 2 O B = 15.1, H 2 O = 

 15.3; Tetragonal; 6=2.9361; 001*101=71 11'; Forms, 

 c(001), m(110), a (100), e (101) ; Cleavage, basal micaceous; 

 Brittle; H. =2-2.5; G. =3.4-3.6; Color, emerald or siskin-green ; 

 Streak, pale green ; Luster, pearly ; Transparent to opaque. 



B.B. Fuses at 2.5 to a black slag and yields water in the closed 

 tube. Reduced with soda, etc., on coal, yields copper buttons. 

 The nitric acid solution shows phosphoric acid with ammonium 

 molybdate, also yields tests for uranium, page 576. 



