SUI.I'IIATKS, CIIROM \TI S, l.TC. 541 



carried down to the lower zones in solution, where it is usually re- 

 depo>ited I >y the action of pyrite as sulphide; hut where conditions 

 favor the evaporation of the solution, it may form the sulphate. 

 The mine waters of liutte, Montana, and at Bisbee, Arizona, con- 

 tain considerable copper in solution as the sulphate, which is re- 

 covered l>y allowing it to run slowly over scrap iron. 



Good specimens are obtained from the ( 'upper (^uei-n mine, Bis- 

 bee, Arixona; and from Isabella mine, Polk County, Tennessee. 



Brochantite, Cu 4 (OH) 6 SO4, is a basic copper sulphate, ortho- 

 rhombic in symmetry, insoluble in water, and without taste ; other 

 tests like chalcanthite ; occurs in the Tintic district, Utah ; Chaffee 

 County, Colorado ; and at several localities in Arizona. 



Owing to its rare occurrence chalcanthite is unimportant com- 

 mercially; the artificial blue vitriol is used in electric batteries, 

 as a fungicide in Bordeaux mixture, and as a mordant in dyeing. 



ALUNITE 



Alunite. KA1 2 (OH) 6 (SO 4 )2.3 H 2 O ; a basic potassium alumin- 

 ium sulphate ; K 2 O = 11.4, A1 2 O 3 = 37.0, S0 3 = 38.6, H 2 O = 13.0 ; 

 Hexagonal; Type, Dihexagonal Alternating ; c = 1.252; 0001 A 

 lOll = 55 19'; lOll.llOl = 90 50'; Cleavage, basal distinct; 

 Brittle ; Fracture, uneven ; H. = 3.5-4 ; G. = 2.58-2.75 ; Color, 

 white, gray, or pale red ; Streak, white ; Luster, vitreous to pearly ; 

 Transparent to opaque; = 1.572; c = 1.592; - o> = .020; 

 Optically (+). 



B.B. Infusible, but may decrepitate when ignited; treated 

 with cobalt solution becomes blue (Al). In the closed tube yields 

 water, and fused in R. F. with soda and a little coal dust yields a 

 sulphur reaction on silver. Insoluble in HC1, soluble in H 2 SO 4 . 



General description. Crystals are small and rhombohedral 

 in habit, usually combinations of several rhombohedrons of the 

 same series. More often massive, granular, or of a fibrous-like 

 structure. 



Alunite is very local in its occurrence, and it has been produced 

 by the action of sulphurous fumes on the feldspars of such rocks as 

 rhyolites, andesites, or trachytes, or by the decomposition of these 

 rocks by percolating waters containing sulphuric acid, as in the 

 Goldfield district of Nevada ; here the formation of alunite has a 

 direct connection with the workable deposits of gold. It also 



