Common Forms of Crystals — 1-a, pyrite; 3, galena; 4-6, calcite; 7-8, 

 feldspar (variety, orthoclase) ; 9, augite; 10, hornblende; 11, a section 

 through figure 9, along a plane perpendicular to the plane of the paper ; 

 12, a similiar section through a hornblende crystal; 13, garnet; 14, gypsum. 



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