OXIDES 



367 



it is the source of all the metallic aluminium, which 

 is ivdun-d. after purification, eloctrolytically from its solution in 

 filled cryolite. While l>:iuxite has been described as a separate 

 Species, it may Ite only a mixture of the other two hydroxides of 

 aluminium, diaspore and gibbsite, as its composition is variable. 

 My metamorphism bauxite forms corundum; in fact corundum 

 wheels are now made from a product obtained by heating bauxite 

 to a high temperature. 



MANGANESE HYDROXIDES 



MANGANITE 



Manganite. MnO(OH) ; Mn 2 O 3 = 89.7, H 2 O = 10.3 ; Ortho- 

 rhombic ; Type, Didigonal Equatorial ; & : b : c = .844 : 1 : .545 ; 

 100 A 110 = 40 10' ; 001 A 101 = 32 50' ; Common forms, c (001), 



I'm. 432. Manganite from the Harz, Germany. 



m (110), 1 (120), d (210) ; Twinning plane e (Oil) common ; Cleav- 

 age, brachypinacoidal perfect, m imperfect; Brittle, fracture 

 uneven ; H. = 4 ; G. = 4.2 4.4 ; Luster, submetallic though 

 bright ; Color, dark steel gray ; Streak, brown to black ; Opaque. 



B.B. Infusible. In the closed tube yields much water. 

 Dissolves in HC1, liberating chlorine; with the fluxes reacts for 

 manganese. 



General description. Nearly always crystalline; in habit 

 elongated parallel to the vertical axis with deep longitudinal stria- 



