io 4 THE PROSPECTOR'S HANDBOOK. 



of a vitreous lustre, found imbedded in lava or basalt. Is 

 harder then felspar, and sometimes equals quartz. S.G. 

 3*3 to 3*5. Dissolves in sulphuric acid, less readily in 

 hydrochloric acid ; the silica gelatinizes. Consists of silica, 

 magnesia, iron, and oxygen. 



MATRICES OF VEINS. 

 The principal ones are : 



Quartz. 



Of nearly every colour, generally white or brownish, 

 sometimes bluish, as in the Queensland gold districts, and 



FIGS. 53 and 54. COMMON CRYSTALS OP QUARTZ. 



of a dull glassy lustre. Scratches glass, &c., but cannot be 

 scratched by a file or knife. Is infusible alone before the 

 B.F., but with carbonate of soda it dissolves to 

 a glass. Is insoluble in acids, except hydro- 

 fluoric. If two pieces of quartz are rubbed 

 together in the dark, a phosphorescent light is 

 seen. When crystallized, is usually in six- 

 sided prisms. H. 7 ; S.G. 2-6 to 2'7. At 

 or near the surface of a lode the quartz has 

 very often a honeycomb appearance, and stained brown, 

 yellow, purple, or other colour, due to decomposed iron 

 or copper pyrites, or other metallic substances, which may 

 be expected to be found deeper down. Quartz is very 

 nearly pure silica. 



