SILICA. 
309 
ARFWEDSONITE. 
[In honor of Professor Arfwedson.] 
Arfwedsonite. Phillips. — Arfvcdsonite. Thomson. — Peritomer Augit-Spath. Mohs. — (Bcudant refers to this 
name as one of the synonyms under his Petalite.) 
Fig. 251. 
Description. Colour pure black, without a shade of green. Streak 
greyish green. It has only been observed in cleavable masses. Primary 
form an oblique rhombic prism.* Fig. 251. M on W 123° 55' (horn¬ 
blende being 124° 30'). Cleavage parallel with the sides of the prism, 
producing more brilliant faces than those of hornblende. Lustre resinous. 
Opaque. Hardness 4.5 (Thomson), 6.0 (Phillips). Specific gravity 
from 3.40 to 3.50. Before the blowpipe, it melts easily, with intume¬ 
scence, into a black globule; with borax, it yields a glass coloured by iron. 
Composition. Silica 50.51, peroxide of iron 35.14, sesquioxide of manganese 8.92, 
alumina 2.49, lime 1.56, moisture 0.96 (Thomson.) 
LOCALITIES. 
Found at Kargardiuarduk in Greenland, associated with sodalite and eudialite. It was 
known by the name of ferruginous hornblende, until it was shown by Mr. Brooke that the 
measurements of its crystals did not agree with those of hornblende. 
A mineral closely agreeing with the description of arfwedsonite, is found associated with 
epidote, garnet and magnetic iron ore, in Putnam county, two miles south of the village of 
Carmel. It has a jet black colour, and is made up of coarse fibres having a high lustre. It 
is less hard than hornblende. Before the blowpipe, it fuses, with some bubbling, into a black 
glass, which is powerfully attracted by the magnet. 
HYPERSTHENE. 
[From the Greek irfep, above , and tfdsvos, strength; because it is harder than hornblende, for which it 
was mistaken.] 
Hypersthene. Hmiy, Cleaveland, Phillips, Thomson and Bcudant. — Paulite. Werner. — Labrador Horn¬ 
blende. Kirwan. — Prismatoidal Schiller Spar. Jameson. — Prismatoidischer Schiller-Spath. Mohs. 
Description. Colour greenish and greyish black; also copper-red and brown. Streak 
greenish grey. It occurs in lamellar concretions, which have a cleavage parallel with the 
diagonals and sides of a rhombic prism of about 93° and 87°, (98° 12' and 81° 48 7 according 
* Dr. Thomson remarks, that as no cleavages can be observed parallel to the base, we are ignorant whether the prism be right 
or oblique. Outlines of Mineralogy, Geology, fyc. 
