KINDS OF ROCKS. 455 
7, Pyrophyllyte and Pyrophyllite Slate — Like the preced- 
ing in appearance and soapy feel, but having the composi- 
tion of pyrophyllite (p. 306). The color is white and gray 
or greenish white. Occurs in North Carolina. One of the 
varieties from the Deep River region is used for slate pen- 
cils. Metamorphic. 
9. TRON-ORE ROCKS. 
1. Hematyte. (Specular Iron Ore).—Hematite (p. 176), in 
metamorphic beds. Color iron. gray, and lustre bright me- 
tallic, but varying to red and jaspery. Has the hardness of 
crystallized hematite and its red streak. Constitutes beds 
of great thickness in Archean regions and thinner beds in 
formations of later geological age; alternates with horn- 
blendic, chloritic, micaceous, and gneissoid, and sometimes 
calcareous rocks, and often contains siliceous or Jjaspery 
layers. 
VARIETIES —a. Jron-gray; the ordinary massive kind. b. Red; 
resembling a hard red jasper, into which it sometimes passes. c. Con- 
taining martite; the octahedral crystals of martite having originaliy 
been magnetite, and showing that they are changed to hematite by 
their red streak. d. Moliated ; sometimes called micaceous iron ore, 
in allusion to the foliation. e. Hpidotic. 
In large beds in the Archean of Canada, St Lawrence Co., N. Y., 
at Marquette, Northern Michigan, Missouri. At Niciaux, in Nova 
Scotia, in semi-metamorphic fossiliferous Devonian there is a bed six 
feet thick. 
2. Itabyryte.—A mica schist consisting largely of hema- 
tite in lamine of bright metallic lustre. 
3. Magnetyte. (dagnetic Iron Ore).—Magnetite (p. 178), 
in metamorphic beds. Color iron gray to grayish black, 
and lustre metallic; never bright red. Strongly attracted 
by the magnet, and hence often separated from the gangue, 
after crushing it, by means of large electro-magnets. Con- 
stitutes, like hematite, thick beds in Archean regions, and 
thinner in rocks of other periods. 
VARIETIES.—a. Massive. b. Granular. c. Epidotic. a. Hornblendic. 
e. Chioritic. f. Titanic. g. Chondroditic; as near Brewster, N. Y., 
where chondroditc is the ‘‘ gangue” of the ore. 
Metamorphic magnetite constitutes thick beds in the Archean of 
Canada, Northern New York, Orange Co., N. Y., Sussex Co., N. J., 
and occurs also in Virginia, cast of the Blue Ridge, in Aibcrmarle, 
