518 MINERALOGY 



WAVELLITE 



Wavellite. A1 3 (OH)3(P0 4 )2 . 5 H 2 ; hydrous basic aluminium 

 orthophosphate ; A1 2 O 3 = 38.0, P 2 O 5 = 35.2, H 2 O = 26.8 ; Or- 

 thorhombic ; Type, Didigonal Equatorial a : b : c = .5573 : 1 : 

 .4084 ; 100 A 110 = 26 47' ; 001 A 101 = 36 36' ; 001 A Oil = 20 

 33'; Common forms, m (110), b (010), p (101) ; Cleavage, p and b 

 quite perfect ; Brittle ; Fracture, uneven ; H. = 3.25^t ; G. = 

 2.3-2.33; Color, shades of green, yellow, white to gray, when 

 impure brown to black ; Streak, white ; Translucent to opaque ; 

 Luster, vitreous to pearly ; -y a = .025 ; Optically ( + ) ; 

 Axial plane = 100; Bx a = c; 2E = 127 2'. 



B.B. Infusible, but whitens and crumbles some what; becomes 

 blue with cobalt solution. The nitric acid solution yields a yellow 

 precipitate with ammonium molybdate (P 2 O 5 ). Soluble in hot 

 strong acids. 



General description. Separate crystals are very rare ; usually 

 occurs in concretionary masses with drusy surfaces and radiated 

 structure ; also stalactitic or in crusts. Small amounts of iron or 

 manganese may replace the aluminium, and while it is not recog- 

 nized in the formula, fluorine is nearly always present. 



Evansite, A1 3 (OH) 6 P0 4 . 6 H 2 O, peganite, A1 2 (OH) 3 PO 4 . 1 H 2 O, 

 and sphasrite, A1 5 (OH)9(PO 4 )2 . 3 H 2 O, are other phosphates of 

 aluminium with varying amounts of water, very closely related to 

 wavellite. 



They are all secondary minerals produced by the interaction of 

 percolating waters, containing phosphates in solution, with argil- 

 laceous shales and slates, in the cracks and cavities of which they 

 occur, never forming deposits of great extent. 



Wavellite is associated with limonite at White Horse Station, 

 Pennsylvania; at Magnet Cove, Arkansas, in fine green radiated 

 aggregates. 



TURQUOISE 



Turquoise. CuO . 3 A1 2 3 . 2 P 2 O 6 . 9 H 2 ; CuO = 9, A1 2 O = 

 36.50, P 2 O 5 = 34.13, H 2 = 20.12 ; Triclinic ;_ a: b : c = .791 : 1 : .605 ; 

 a = 92 58', P = 9_3 30', -y = 107 41'; 010 A 100 = 44 50'; 100 

 A 110 = 31 10_; Oil A ilO = 105 36'; Forms b (010), a (100), 

 m(110), M(110), k(011); Cleavage, marked; Brittle; Fracture, 



