454 DESCRIPTIONS OF ROCKS. 



feldspar intimately blended, and often contains crystals 

 (usually octahedrons) of magnetite, and sometimes chlorite 

 in distinct scales or concretions. Metamorphic. 



Varieties. — a. Ordinary, b. Hornblendic ; the hornblende ingrains 

 or needles, c. Magnetitic. d. Tourmalinic. e. Gametiferous. f. Fyr- 

 oxenk. g. Staurolitic. h. Epidotic. Graduates into argillyte. 



2. Chlorite- Argillyte. — An argillyte or phyllyte consist- 

 ing largely of chlorite. Metamorphic. 



3. Talcose Schist. — A slate or schist consisting chiefly of 

 talc. Not common, except in local beds, most of the so- 

 called "talcose slate" being hydromica schist (p. 440). 



4. Steatyte, Soapstone (p. 55). — Consists of talc. Mas- 

 sive, more or less schistose ; granular to aphanitic. Color, 

 gray to grayish-green and white. Feels very soapy. Easily 

 cut with a knife. Metamorphic. 



Varieties. — a. Coarse-granular, and massive or somewhat schis- 

 tose, b. Fine-granular ; "French chalk." c. Aphanitic, or Rens- 

 selaerite; of grayish-white, greenish, brownish to black colors, from 

 St. Lawrence County, N. Y. , and Grenville, Canada. 



5. Serpentine. — Aphanitic or hardly granular ; of dark- 

 green to greenish-black color, easily scratched with a knife, 

 and often a little greasy to the feel on a smooth surface. 

 Although generally dark green, it is sometimes pale grayish 

 and yellowish-green, and mottled. Metamorphic. 



Varieties. — a. Noble; oil-green and translucent, b. Common; opaque, 

 and of various colors, c. Schistose, d. Diallagic; contains green or 

 metalloidal diallage. e. Ghromiferous; contains chromite, a chromium 

 ore belonging to serpentine regions, f . Bnstitic ; contains bastite or 

 enstatite. g. Gametiferous ; contains garnet, as at Zoblitz. h. Chry- 

 solitic ; contains chrysolite, i. Brecciated ; consists of united frag- 

 ments. (See also page 308.) Serpentine has been made by the altera- 

 tion of chrysolite beds, and of chondrodite and other magnesian sili- 

 cates. A rock consisting of serpentine and saussurite is true Gdbbro. 



6. Ophiolyte (Verd- Antique Marble). — A mixture of ser- 

 pentine with limestone, dolomite, or magnesite, having a 

 mottled green color. Often contains disseminated magne- 

 tite or chromite. Metamorphic. 



Varieties. — a. Calcareous ; the associated carbonate being calcite. 

 b. Dolomitic ; the associated carbonate, dolomite, c. Magnesitic ; the 

 associated carbonate, magnesite. Either of these kinds may contain 

 chromite or magnetite. Handsome verd-antique marble has been ob- 

 tained near New Haven and Mil ford, Conn. A beautiful variety, hav- 

 ing pure serpentine disseminated in grains or spots through a whitish 

 calcite, occurs at Port Henry, Essex County, N. Y., and is worked. 



