488 DESCRIPTIONS OF ROCKS. 
damourite, and. the black mica is usually biotite, though 
occasionally the allied, more iron-bearing, species, lepidome- 
lane. Oligoclase or albite is very often present. 
Occurs both metamorphic and eruptive. Metamorphic 
granite may often be seen graduating into gneiss, or lying 
in beds alternating with gneiss. 
VARIETIES.—There are, A Muscovite granites ; B. Biotite granites ; 
C. Muscovite-and-biotite granites, the last much the most common. 
The most of the following varieties occur under each except the horn- 
blendic, which is usually a Biotite, or Muscovite-and-Biotite, granite. 
There is also, D. Hydromica-granite. a. Common or Ordinary granite ; | 
the color is grayish or flesh-colored, according as the feldspar is white 
or reddish, and dark gray when much black mica is present. Granite 
varies in texture from fine and even, to coarse ; and sometimes the 
mica, feldspar, and quartz—especially the two former—are in large 
crystalline masses. An average granite (mean of 11 analyses of Lein-- 
ster granite, by Haughton) affords Silica 72-07, alumina 14°81, iron 
protoxide and sesquioxide 2°52, lime 1°68, magnesia 0°33, potash 5-11, 
soda 2°79, water 1:09=100°35. b. Porphyritic granite ; has the ortho- 
clase in defined crystals, and may be (a) small porphyritic, or (/) large 
porphyritic, and have the base (yv) coarse granular, or (6) fine, and 
even subaphanitic. c. Albitic granite; contains some albite, which is 
usually white. d. Oligoclase granite (Miarolite) ; contains much oligo- 
clase. e. Microcline granite ; contains the potash triclinic feldspar, 
microcline. f. Hornblendic granite ; contains black or greenish-black 
hornblende, along with the other constituents of granite. g. Black 
micaceous granite ; consists largely of mica, with defined crystals 
of feldspar (porphyritic), and but little quartz. h. Jolitic; con- 
taining iolite. i. Globuliferous granite ; contains concretions which 
consist of mica, or of feldspar and mica. j. Gncissoid granite; a 
granite in which there are traces of stratification; graduates into 
gneiss. k. Pegmatyte, or Graphic granite ; consists mainly of ertho- 
clase and quartz, with but little mica ; but the quartz is distributed 
through the feldspar in forms lccking like oriental characters. 
A porphyritic granite, cecurring at the junction of the andalusite 
mica-argillyte (page 441) of the White Mountain Notch, N. H., with 
the Mt. Willard granite, on the west side of Mt. Willard, conformable 
with the bedding of the argillyte, has the argillyte for its base ; and 
in it the orthoclase is in large well-defined crystals, and the quartz 
in double six-sided pyramids, both easily separable from the matrix ; 
the layer is six to twenty feet thick. 
The distinctions as to kinds of rocks between metamorphic and 
eruptive granites are not yet made out. A porphyritic variety, having 
the base fine-grained, occurs east of Parkview Peak, in the Recky Mts., 
which, according to Hague, is eruptive and related to the trachytes of 
the region. The granite of New England is for the most part meta- 
morphic or in veins. The following are prominent regions of the 
granite quarries. In Maine: at Hallowell, a whitish granite, some- 
times a little gneissoid ; at Rockport, whitish ; at Clarke’s Island, 
spotted gray ; at Jonesbury, flesh-red ; also in the Mt. Desert region. 
