72 LITHOLOGICAL GEOLOGY. 



Zealand, and in North Carolina. Lherzolyte (p. 70) is chrysolite and pyroxene. 

 Picryte, from Moravia, is half chrysolite, the rest feldspar, diallage, hornblende, and 

 magnetite. Ossipyte (p. 70) is chrysolite and labradorite. (Peridotyte is a chrysolitic 

 rock of igneous origin.) Chrysolite rocks are sometimes partly altered to serpentine. 



5. Hydrous Magnesian Series. 



The hydrous magnesian series, characterized by the presence of the 

 hydrous magnesian minerals talc, serpentine, or chlorite (p. 55), ranges 

 from a granite-like rock called protogine (containing the constituents 

 of granite, excepting talc or chlorite in place of mica) down to the 

 semicrystalline talcose and chlorite slates ; and also to compact flinty 

 rocks near aphanite. Besides these, there are the serpentine rocks. 

 Talc and serpentine are silicates of magnesia and water alone, while 

 chlorite contains also alumina and oxyd of iron. The chloritic rocks, 

 consequently, often abound in hornblende, and are frequently asso- 

 ciated with rocks of the hornblendic series. The 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, 

 usually gneissoid in structure and really a kind of gneiss, consisting of 

 quartz, feldspar, and chlorite (or talc ? ), with sometimes a little mica 

 (micaceous protogine). The feldspar may be orthoclase or oligoclase, 

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

 Color, grayish white or greenish white. A protogine occurs at Lit- 

 tleton, N. H., in Devonian beds, which contains a serpentine-like 

 mineral in disseminated grains. 



(3.) Talcose Slate. — A slaty rock, soapy to the touch, consist- 

 ing largely of talc or soapstone. Not common, except in local beds. 

 The most of the rocks that, have been called talcose slates are hydro- 

 mica slates (p. 54). 



(4.) Steatyte, or Soapstone (p. 55). — A massive, more or less 

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

 feel, very soapy ; composition, that of talc. 



Rensselaeryte is soapstone of compact texture, and either gray, whitish, greenish, 

 brownish, or even black, color. Oceurs in the towns of Fowler, De Kalb, Gouverneur, 

 and others, St. Lawrence Co., N. Y., and also in Grenville, Canada. 



(5.) Chlorite Slate. — Slaty, of a dark green to greenish-black and 

 grayish-green color ; but little if any greasy to the touch, and little 

 shining. Consists of chlorite, quartz, and often more or less feldspar. 

 Sometimes contains chlorite in scales, or in concretions ; frequently it 

 is micaceous ; there often occur in it hornblende, magnetite ; some- 

 times tourmaline, garnet, pyroxene. 



(6.) Chloritic Argillyte, Chlorargilhjte. — Argillyte like that described on p. 69, but 

 consisting in part of chlorite, and showing it in its proportion of iron and water, and 

 in its specific gravity, while not in color or texture. Here belongs some roofing-slate. 



