KINDS OF ROCKS. 81 



color of the rocks is some shade of dull grayish, brownish, olive, or 

 blackish green. Specific gravity, 2.4 to 3 ; or over 3 if containing 

 hornblende. 



(1.) Protogine. — A granular crystalline or granite-like rock, con- 

 sisting of quartz, feldspar, and talc, with sometimes some mica 

 (micaceous protogine). The feldspar may be orthoclase or oli- 

 goclase, or both (both in the Alps), and is sometimes in distinct 

 crystals (porphyry). Color, grayish white or greenish white. 

 Gneissoid protogine is a gneiss-like rock, consisting of quartz, 

 feldspar, and talc, between talcose schist and gneiss in its charac- 

 ters. Occurs in the Alps. 



(2.) Chloritic Gneiss. — A gneissoid rock consisting of quartz and feldspar, 

 and often mica, with soft olive-green granular chlorite distributed through it in 

 small patches. 



(3.) Talcose Schist. — A slaty rock, less crystalline than mica 

 schist, and less evenly schistose, characterized by a slight greasy 

 feel, glistening and talcose look upon the surface of the slate, a 

 greenish-gray or grayish-green to brown color. Texture usually 

 near that of argillite, sometimes with quartz and feldspar in grains 

 like mica schist. It passes on one side into schistose talc, which is very 

 greasy to the feel, and is pure talc ; and on the other into argillite, 

 or mica schist. Frequently contains actinolite, garnet, staurotide, 

 tourmaline, pyrites ; and the intersecting or intercalated quartz 

 often contains gold. 



(4.) Steatite, or Soapstone ($ 66). — A massive, more or less 

 schistose rock, fine-granular ; color, gray to grayish-green ; feel, 

 very soapy ; composition, that of fine talc. Often contains crys- 

 tals of tourmaline (p. 58), dolomite, or brown spar (p. 63), or mag- 

 netite (p. 65). 



Rensselaerite is a kind of soapstone, of compact texture, and either gray, 

 whitish, greenish, brownish, or even black, color. For an analysis by T. S. 

 Hunt, see Logan's Rep. for 1853-56, p. 483. Occurs in the towns of Fowler, 

 De Kalb, Gouverneur, and others, St. Lawrence co., N.Y., and also in Gren- 

 ville, Canada. 



(5.) Chloritic Schist. — A more or less slaty rock, like the pre- 

 ceding, but of an olive-green or greenish-black color, though some- 

 times pale greenish-gray ; it is somewhat less greasy to the feel, 

 usually less shining ; the chlorite fine-granular and soft ; sometimes 

 in deep-green mica-like scales or plates. Often contains black and 

 dark-green hornblende in acicular and grouped crystals and fibrous 

 masses, also magnetite in octahedral crystals. Graduates into horn- 

 blendic slate. A rock of this kind from Potton, Canada, analyzed 



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