File:A popular guide to minerals - with chapters on the Bement Collection of minerals in the American Museum of Natural History, and the development of mineralogy (1912) (14755082856).jpg

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Title: A popular guide to minerals : with chapters on the Bement Collection of minerals in the American Museum of Natural History, and the development of mineralogy
Year: 1912 (1910s)
Authors: Gratacap, L. P. (Louis Pope), 1851-1917
Subjects: American Museum of Natural History. Bement Collection of Minerals Mineralogy
Publisher: New York : D. Van Nostrand
Contributing Library: Robarts - University of Toronto
Digitizing Sponsor: University of Toronto

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a new gem of great beauty. Thecrystals are flat spear-shaped transparent sheets, rounded withwrinkled edges and of great size. Petalite, a lithia mineral has been found in Maine in whitecolorless glassy masses, and in southern California, in associationwith the lithia bearing minerals of that prolific locality. Amphibole, with its related species and the series of mineralvariations included under this one name, forms a parallel sectionto pyroxene, containing, however, fewer species and less crystal-lographic variety. The prism in Amphibole is flattened, havingan angle of 56° and 124°, and in chemical constitution Amphi-bole, very generally, contains more magnesia and alkalies thanpyroxene. The separation of its varieties under aluminous andnon-aluminous groups obtains as in pyroxene. The aluminoussection embraces Edenite, Pargasitc, Hornblende; and the non-aluminous, Tremolite, Actinolite (nephrite, asbestus, smaragdite),Cummingtonite, Dannemorite, Richtcritc, most of which are rep-
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MALACHITE Bisbee, ArizonaBement Collection, American Museum of Natural History GUIDE TO COLLECTIONS 1^9 resented by specimens in the cabinet. Amphibole, like Pyroxene,is a very widely distributed species and forms rock masses, en-tering into the composition of both metamorphic and igneous rocks,as well as local mineral crystallizations. Amphibole is subject toalteration, especially in the more fibrous varieties, and by taking upwater, with a concentration of magnesia, becomes changed to talc,serpentine and chlorite. Cabinets usually contain an instructive series of specimens, il-lustrating the very divergent lines of variation in external appear-ance which are developed in this species. Amongst these thepeculiar woollike bundles of fibres of Breislakite from Vesuvius,Italy, the Asbestus from New York Island and the Tyrol, thewoven, feltlike plates and masses of Mountain Leather, the radi-ating centers of Hydrous Anthophyllite, the mossy surfaces ofByssolite (St. Gothard, Switzerland),

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