Elements of mineralogy, crystallography and blowpipe analysis from a practical standpoint .. . Crystallization.—Hexagonal. Hemimorphic class,Axis c = Prevailing forms : trigonal prism in, second order prism «, unitrhombohedron p, negative rhombohedron f = a : co a : a : are: pp = 133° 8;#= 103° ; mp = iiy° 20. Optically—. Strongly dichroic, absorption very marked for raysvibrating parallel to the vertical axis. Double refraction ratherstrong. Physical Characters. H., 7 to Sp. gr,, to , vitreous or resinous. Transparent to opaque. Streak, white. Tenacity, b
Elements of mineralogy, crystallography and blowpipe analysis from a practical standpoint .. . Crystallization.—Hexagonal. Hemimorphic class,Axis c = Prevailing forms : trigonal prism in, second order prism «, unitrhombohedron p, negative rhombohedron f = a : co a : a : are: pp = 133° 8;#= 103° ; mp = iiy° 20. Optically—. Strongly dichroic, absorption very marked for raysvibrating parallel to the vertical axis. Double refraction ratherstrong. Physical Characters. H., 7 to Sp. gr,, to , vitreous or resinous. Transparent to opaque. Streak, white. Tenacity, brittle. Color, black, brown, green, blue, red, , difficult, parallel to R and i-2. Before Blowpipe, Etc.—Usually fuses, sometimes very a paste of KHS04,CaF2 and water it yields a green in acids, but after strong ignition gelatinizes. Similar Species.—Differs from hornblende in hardness, crystal-line form and absence of prismatic cleavage. Differs from garnetor vesuvianite in form, difficult fusion, and green flame. Remarks.—Occurs
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