334 
DESCRIPTIVE MINERALOGY. 
hexaedre of Haiiy, Fig. 301 ; the same with the obtuse solid angles replaced by single planes, 
unibinaire of Haiiy, Fig. 302, and Fig. 303. The twin crystal, Fig. 304, geminee obliqaangle 
Fig. 301. Fig. 302. Fig. 303. 
Fig. 304. 
of Hairy, has also been observed at this locality, although it is usually imperfect. M on M' 
129° 30'; M or M' on P 90° ; M on o 115° 18'; M or M' on r 137° 58b 
New-York County. Three and a half miles from the city, on the banks of the Hudson, 
this mineral is found in mica slate. It has the form of short but very perfect rhombic prisms, 
with the acute lateral edges replaced by tangent planes, and terminated by dihedral summits 
(Fig. 303), and sometimes forming an imperfect cross.* 
Staurolite probably occurs also in the counties of Rockland and Westchester. I have found 
it in bowlders of mica slate on the banks of the Hudson, at Nyack. These bowlders more 
nearly resembled the rocks found in Westchester, than those of Rockland. 
This mineral has been observed in the mica slate in Massachusetts and Connecticut. 
FELDSPAR. 
[From the German Feldspath, Jieldspar; probably from its being often found loose on the surface 
of the ground.] 
Feldspar. Thomson, Shepard and Dana. — Prismatic Felspar, or Common Felspar. Jameson. — Orthotomer 
Feld-Spath. Mohs. — Orthose. Beudant. — Felspar. Phillips. 
Fig. 305. 
Description. Colour white, grey, green, blue, red and brown, 
sometimes with a pearly opalescence. Streak greyish white. It 
occurs regularly crystallized; and also massive and disseminated. 
The primary form is a doubly oblique prism. Fig. 305. M on T 
120° 35'; P on M 90° ; P on T 67° 15b Cleavage parallel with P 
and M perfect; with T obscure, though sometimes easily obtained. 
Fracture conchoidal, splintery, slaty and earthy. Lustre vitreous or 
vitreo-pearly. From transparent to opaque. Brittle. Hardness 6.0. 
Specific gravity from 2.39 to 2.58. Before the blowpipe, on char- 
Pierce and Torrey. Cleaveland’s Mineralogy. 
