CARWNATI S 





General description.- Crystal* MIT tabular, pyramidal, or 



rloniiated prismatic in habit. When pyramidal in habit, like other 

 member- of the group, 

 they an- pseudo-hexagonal 

 in appearance, from the 

 equal development of the 

 pyramid and brachydome, 

 as at Mies in Bohemia. 

 When tabular, it is very 

 apt to form stellate groups 

 by repeated twinning after 

 the aragonite method, but 

 here the space between in- 

 dividuals is not completely 

 filled as in aragonite, as at 

 Mies and Pribram, Bo- 

 hemia. When elongated in 

 habit, the prism zone is 

 deeply striated lengthwise, 

 as at the old Wheatley 

 Mine, Chester County, and Phoanixville, Pennsylvania. It occurs 

 also in crusts, stalactitic, granular, or massive, often colored green 

 or blue with copper carbonates. 



Cerussite is associated as a secondary product in the superficial 

 areas of lead deposits where it is formed from galena by oxidation 

 and the action of carbonated waters, which may also form carbon- 

 ates from anglesite, the sulphate of lead, after which many pseudo- 

 morphs are found. 



Next to galena cerussite is the most important ore of lead and 

 is mined at Leadville, Colorado; Arizona; and Utah. 



Artificially it may be formed as aragonite. 



FIG. 451. Cerussite, Twins. Mies, Bohemia. 



MALACHITE 



Malachite. Basic carbonate of copper, (Cu.OH) 2 C0 3 ; CuO 

 = 71.9, CO 2 = 19.9, H 2 O = 8.2; Monoclinic; Type, Equato- 

 rial ; & : b : c = .881 : 1 : .401 ; p = 61 50' == 001 A 100 ; 100 A 110 

 = 37 50'; 001 A Oil = 19 29'; Common forms, c(001), a (100), 

 b(010), m (110); Twinning plane, 100; Cleavage, basal perfect, 

 b less so; Brittle; Fracture, uneven; H. = 3.5-4; G. = 3.9-4; 

 Color, bright green; Streak, pale green; Luster, vitreous, silky 



