310 
DESCRIPTIVE MINERALOGY. 
to Necker.) Fracture uneven. Lustre bronze-metallic upon the most perfect diagonal clea¬ 
vage ; in other directions, more or less vitreous. Opaque or slightly translucent on the edges. 
Hardness 6.0. Specific gravity from 3.338 to 3.385. Before the blowpipe it is infusible 
per se, but melts upon charcoal into a greenish grey opaque globule; with borax, it melts 
into a greenish glass. It is unacted on by acids. 
Composition. Specimen from Labrador —Silica 54.25, magnesia 14.00, alumina 2.25, 
lime 1.50, oxide of iron 24.50, water 1.00 {Klaproth). It is therefore a silicate of magnesia 
and iron. 
Geological Situation. It is usually found in primitive rocks, especially those of a gra¬ 
nitic character. It has also been observed in greenstone. 
It may be here remarked, that there is some uncertainty in regard to this mineral. Dr. 
Kohler of Cassel, some years since, examined several varieties of diallage, and inferred 
from his analyses that metalloidal diallage, bronzite and hypersthene, are subspecies of 
pyroxene, and not, like schiller spar and anthophyllite, species of the schiller spar family.* 
Among these analyses, that of the metalloidal diallage approaches more nearly that of our 
so called hijpersthene from Lake George, to be presently noticed, than any other. Mr. J. 
Phillips expresses the opinion that hypersthene and diallage often differ from each other 
rather by the crystalline arrangement of the parts, or the substitution of mutually replacing 
substances, than by any essential and constant characters.! 
LOCALITIES. 
Essex County. According to Dr. Emmons, hypersthene is very abundant in what are 
termed the granite rocks of this county. It is associated with labradorite. He does not 
decide whether it is identical with the hypersthene rock of Dr. MacCulloch ; but he says it 
is as truly one of the constituents of this rock as mica or quartz in the common granite, 
though not so generally diffused. He also states that the most valuable beds of magnetic iron 
ore in Essex, and the other northern counties, occur in hypersthene rock.! 
Washington County. A specimen which was obtained from the banks of Lake George 
in the town of Putnam, and about two miles from Ticonderoga, closely resembles the so 
called hypersthene from the more northern counties. Its colour is from ash-grey to black. 
It is foliated and lamellar, and has a pearly or metallic lustre on the cleavage faces. The 
streak is white. Its hardness is less than that of pyroxene. 
The following are the constituents of this mineral, viz: 
Silica,.... 45.45 
Lime,.... 24.33 
Magnesia,. 18.00 
Oxide of iron,. 11 »49§ 
* Brewster's Edinburgh Journal of Science. IX. 3G1. f Phillips Geology. II. 63. 
t Emmons. Nexo-York Geological Reports, 1838 and 1840. 
(j The above mineral exactly resembles the so called hypersthene from near Wilmington, Delaware. The latter is magnetic. 
