352 MINERALOGY 



like color in artificial teeth. Titanium trichloride is replacing 

 stannous chloride as a mordant in cloth printing. Ferro-titanium 

 is used to produce a hard steel, with a high transverse and tensile 

 strength; this more recent use may in the near future increase 

 the demand for titanium minerals. 



PYROLUSITE 



Pyrolusite. Dioxide of manganese, MnO 2 ; Mn = 63.2, 

 O = 36.8 ; Amorphous but often in pseudomorphs ; H. = 2-2.5, 

 soils paper ; G. = 4.82 ; Color and streak, black ; Luster, metallic 

 to dull, -opaque. 



B.B. Infusible, shows manganese with the fluxes. In the 

 closed tube yields little or no water. Dissolves in HC1 with the 

 liberation of chlorine. 



General Description. Massive, compact, fibrous, stalactitic, 

 or dendritic. Oxides of manganese are usually associated with iron 

 ores, having been formed in many cases by the interaction of the 

 same agents. Pyrolusite is formed from hydrated oxides of man- 

 ganese by loss of water. It has been thought that pyrolusite may 

 be orthorhombic in symmetry, but it is probable that such crystals 

 are pseudomorphs derived from manganite by the expulsion of its 

 water. 



Oxides of manganese are concentrated at many localities either 

 by replacement or by precipitation from solutions resulting from 

 the decomposition of silicates or carbonates containing manganese. 

 Such deposits are associated with limestone and sedimentary forma- 

 tions, or form irregular pockets and nodules in clays. Such deposits 

 extend all along the Appalachian and Piedmont regions, where they 

 are mined commercially in the Blue Ridge Mountains of Virginia, 

 and at Cartersville, Georgia. Pyrolusite is also mined at Bates- 

 ville, Arkansas ; and Livermore, California. Cabinet specimens are 

 obtained at Salisbury, Connecticut, and Stockbridge, Massachu- 

 setts. 



QUARTZ 



Quartz. Silicon dioxide, SiO 2 ; Si = 46.7, O = 53.3 ; Hexag- 

 onal; Type, Trigonal Holoaxial ; c = 1.100; Common forms, 

 m (1010), r (1011), z (OlTl), x (5161),_ s (1121) ; 0111 A 0110 = 38 

 13';, 1010 A 5161 = 12 1'; 10lO A 1101 = 38 18' Cleavage, r 

 perfect but difficult; Brittle, fracture conchoidal; H. = 7; G. = 



