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 in grains 
or necdles. c. Mugnetitic. d. Tourmaiinic. e. Gurnetiferous. f. Pyr- 
oxenic. g. Staurolitic. h. Hpidotic. Graduates into argillyte. 
gillyte or phyliyte 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 tale. Mas- 
sive, more or less schistose ; granular to aphanitic. Color, 
gray to grayish-green and white. Feels very soapy. Hasily 
cut with a knife. Metamorphic. 
VARIETIES. —a. Coarse-granular, and massive or somewhat schis- 
tose. b. Fine-granular; ‘French chalk.” c. Aphanitic, or Rens- 
seluerite; 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. NVobdle; oil-green and translucent. b. Common; opaque, 
and of various colors. c. Schistos2. d. Diallagic ; contains green or 
metalloidal diallage. e. Chromiferous; contains chromite, a chromium 
ore belonging to serpentine regions. f. Bustitic ; contains bastite or 
enstatite. g. Garnetiferous ; 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 Gabbro. 
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 Milford, 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. 
