. Bulletin - New York State Museum. Science. 104 NEW YORK STATE MUSEUM Cyanite (disthene) Al2Si05 Cyanite is probably a basic rnetasilicate of aluminium with the formula (A10)2 Si03. Dana, however, places it for conveni- ence in the group with sillimanite, to which bears a close relation. Cyanite is found in long bladelike, triclinic crystals which are rarely terminated and in coarsely bladed columnar masses usu- ally of a grayish blue color (pi. 22). It cleaves easily parallel to the three pinacoids. The luster is vitreous to pearly and the color commonly blue along the center of t
. Bulletin - New York State Museum. Science. 104 NEW YORK STATE MUSEUM Cyanite (disthene) Al2Si05 Cyanite is probably a basic rnetasilicate of aluminium with the formula (A10)2 Si03. Dana, however, places it for conveni- ence in the group with sillimanite, to which bears a close relation. Cyanite is found in long bladelike, triclinic crystals which are rarely terminated and in coarsely bladed columnar masses usu- ally of a grayish blue color (pi. 22). It cleaves easily parallel to the three pinacoids. The luster is vitreous to pearly and the color commonly blue along the center of the blades^ shading to white on the edges; also gray, green to nearly black. It occurs in gneiss and mica schist with garnet and staurolite and is often associated with corundum. It is found in the cor- undum regions of Massachusetts, Pennsylvania, North Caro- lina and Georgia; it has been noted in the rocks of New York island. Cyanite is sometimes used as a gem. Datolite Ca(B0H)Si04 Datolite is a basic calcium and boron orthosilicate. It crystallizes in monoclinic forms of varied habit but usually short prismatic (fig. 226) and often highly modified. The crystals are glassy, transpa- rent or translucent and colorless, white or pale green. A massive compact variety has a dull luster resembling unglazed porcelain and is gray or pinkish in color. Datolite occurs as a secondary mineral in veins and cavities in basic eruptive rocks asso- ciated with calcite, prehnite and the zeolites; also in metallic veins as in the Lake Superior copper region where the massive variety is quite common. It is also found in the vicinity of Bergen Hill and Paterson N. J. and in other localities through- out New York1 and New England. Epidote HCa2(ALFe)3Si3013 Epidote is a basic calcium, aluminium and iron silicate. It occurs in monoclinic crystals which are commonly elongated 1 A few rare occurrences are noted in St Lawrence county. See Dana, J. D. System of mineralogy. Please note that these i
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