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FELDSPAR 177 



Middletown, Conn. ; South Royalston and Barre, Mass., 

 besides numerous other localities. Green feldspar occurs at 

 Mount Desert, Me. ; an aventurine feldspar at Leyperville, 

 Penn. ; Adularia at Haddam and Norwich, Conn., and Par- 

 sonsfield, Me. A fetid feldspar (sometimes called necronite) 

 is found at Rogers' Rock, Essex county ; at Thomson's 

 quarry, near 196th street New York city, and 21 miles from 

 Baltimore. Carlsbad and Elbogen in Bohemia, Baveno in 

 Piedmont, St. Gothard, Arendal in Norway, Land's End, and 

 the Mourne mountains, Ireland, are some of the more inter- 

 esting foreign localities. 



The name feldspar is from the German word f eld, mean- 

 fagjield. 



Uses. Feldspar is used extensively in the manufacture of 

 Porcelain. Moonstone and Sunstone are often set in jewelry. 

 They are polished with a rounded surface, and look some- 

 what like cat's-eye, but are much softer. 



Kaolin. This name is applied to the clay that results 

 from the decomposition of feldspar. It is the material used 

 for making porcelain or china ware. The change the feld- 

 spar undergoes in producing kaolin consists principally in a 

 removal of the alkali, potash, with part of the silica and the 

 ^addition of water. | Composition of a specimen from Schnee- 

 berg, silica 43*6, alumina 37*7, peroxyd of iron 1*5, water 

 12*6, (Berthier.) It occurs in extensive beds in granite re- 

 gions, where it has been derived from the decomposition of 

 this rock. A granite containing talc seems to be the most 

 common source of it. See farther, the chapter on Rocks. 



ALBITE. 



Triclinic. In modified oblique rhomboidal prisms* 

 M : T=422 15', P : T=115° 5 ; P : M=110° 

 51'. The crystals are usually more or less thick 

 and tabular._^Also massive, with a granular or 

 ' laln^ttaTstructure. Laminae brittle. 



Color white ; occasionally light tints of bluish 

 white, grayish, reddish and greenish. Luster 

 vitreous to pearly, and sometimes a bluish opalescence is 

 exhibited. Transparent to subtranslucent.^ H=6. Gr= 

 2-6—2-7. m . ** 



What are the uses of feldspar 1 What is kaolin, and for what is it 

 used ? What is the crystallization and appearance of albite ? 



