398 



MINERALOGY 



to dull and earthy; Translucent to opaque; |3 = 1.87; Optically 

 (-) ; Axial plane parallel to 010; Bx aA c = 23 39' in front; 2E = 



89 18' ; 2 V = 44 7'. 



B.B. Blackens and 

 fuses. In R. F. on coal 

 yields copper and a 

 green flame. In the 

 closed tube yields 

 water, dissolves in 

 dilute HC1 with effer- 

 vescence, yielding car- 

 bon dioxide. 



General description. 

 Crystals are seldom 

 distinct individuals, 

 but grouped in tufts, 

 divergent or elongated, 

 acicular, and radiated, 

 as at Betzdorf, in 

 Westphalia; also bot- 

 ryoidal, stalactitic, 

 nodular, and curvi- 

 linear masses, formed 

 with concentric layers 

 of different shades of 

 green, are common, as 

 at Bisbee, Arizona. 

 Malachite is a second- 

 ary mineral formed 

 as an oxidation prod- 

 uct of other copper ores, as cuprite, chalcocite, chalcopyrite, or 

 melaconite, by the action of percolating waters charged with 

 carbon dioxide, and is characteristic of the surface workings of 

 all copper deposits. Numerous pseudomorphs of malachite, 

 especially after cuprite, occur, as at Chessy near Lyons, France, 

 where there are beautiful examples of octahedrons and rhombic 

 dodecahedrons, some of which are only coated with a crust of 

 carbonate, while the interior is still unaltered cuprite. Octahedral 

 pseudomorphs are also found at Bisbee, Arizona. 



Malachite is of common occurrence in many copper localities ; 



