Elements of mineralogy, crystallography and blowpipe analysis from a practical standpoint .. . Hausmannite, pji = 105° 26 hausmannite. Composition.—MnjO^. (MujOj , MnO per cent.). General Description.—Black granular strongly coherent masses occasionally insimple and twinned tetragonal pyramids which are more acute than those of braunite,c= Physical Characters.—Opaque. Lustre, submetallic. Color, brownish , chestnut brown. H., 5 to Sp. gr., to Strongly coherent. Before Blowpipe, Etc.—Infusible. C-jlors borax bead amethystine. Solublein hydrochloric aci
Elements of mineralogy, crystallography and blowpipe analysis from a practical standpoint .. . Hausmannite, pji = 105° 26 hausmannite. Composition.—MnjO^. (MujOj , MnO per cent.). General Description.—Black granular strongly coherent masses occasionally insimple and twinned tetragonal pyramids which are more acute than those of braunite,c= Physical Characters.—Opaque. Lustre, submetallic. Color, brownish , chestnut brown. H., 5 to Sp. gr., to Strongly coherent. Before Blowpipe, Etc.—Infusible. C-jlors borax bead amethystine. Solublein hydrochloric acid with evolution of chlorine. Similar Species.—Differs from braunite in hardness, streak and absence of silica. 2l6 DESCRIPTIVE MINERALOGY. PYROLUSITE.—Black Oxide of Manganese. Composition.—MnOj, (Mn per cent). Fig. Florence, Italy. General Description.—^Asoft black mineral of metalliclustre. Frequently composedof fibres or columns often ra-diated, but also found finegrained, massive, stalactitic,and as velvety crusts. It isalso the common 415. Usually soils thefingers. Frequently in alter-nate layers with psilomelane. Physical Characters. H., i to , metallic or , , black to steel gray. Sp. gr., 4-7 to 4-86. Opaque. Tenacity, rather brittle. Before Blowpipe, Etc.—Infusible, becomes brown. Usuallyyields oxygen and a little water in closed tube. Colors boraxbead amethystine. Soluble in hydrochloric acid with evolution ofchlorine. Similar Species.—Distinguished by its softness and black streakfrom other manganese minerals. Remarks.—Pyrolusite results from the dehydration of manganite and the altera-tion of alabandite and rhodochrosite. It is usually with psilomelane, hematite, limon-ite or manganite. By far the larger part of all that is mined i
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