SILICA. 



309 



ARFWEDSONITE. 



[In honor of Professor Arfwedson.] 



AifWedsonite. Phillips. — Arfvedsonite. Thomson. — Pcritomer Augit-Spath. Mohs. — (Beudant refers to this 

 name as one of the synonyms under his Petalite.) 



Fig. 251. 



M 



M 



Description. Colour pure black, without a shade of green. Streak 

 greyish green. It has only been observed in cleavable masses. Primary 

 form an obhque rhombic prism.* Fig. 251. M on M' 123° 55' (horn- 

 blende being 124° SCK). 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 oi 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 i*£p, above, and rf^svof, strength ; because it is harder than hornblende, for which it 



was mistaken.] 



Hypcrsthene. Haay, CUaveland, PhiUips, Thomson and Beudant. — 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' 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. Otalina of Miruralogi/, Geology, 4«. 



