BISILICATES. Q45, 
of a white color, along with garnet ; at Boonville, in bowl- 
ders with garnet and pyroxene ; Grenville. Lower Canada ; 
in Bucks County, Pennsylvania ; at Keweenaw Point, Lake 
Superior. Hdelforsite is impure wollastonite. 
Pyroxene.— Augite. 
Monoclinic. 7 A J=87%° 5’; cleavage perfect parallel with 
the sides of this prism, and also distinct parallel with the 

diagonals. Usually in thick and stout prisms, of 4, 6 or 8 
sides, terminating in two faces meeting at an edge. JAi-t 
139 33, / A 1-0-2136" 275 LA 1=120° 32% Massive varie- 
ties of a coarse lamellar structure ; also fibrous, fibres often 
very fine and often long capillary. Also granular, usually 
in coarse granular and friable masses ; grains usually angu- 
lar ; sometimes round ; also compact massive. 
Colors green of various shades, verging to white on one 
side and brown and black on the other, passing through 
biue shades, but not yellow. Lustre vitreous, inclining to 
resinous or pearly ; the latter especially in fibrous varieties. 
Transparent to opaque. H.=5-6. G.=3°2-3°8. 
Composition. KO,Si; in which R may be Ca, Mg, Fe, 
Mn, and sometimes Zn, K,, Na,, these bases replacing one 
another without changing the crystalline form, of which 
two or more are usually present ; the first three are most 
common. Calcium is always present. The following is an 
analysis of a typical variety : Silica 55:0, lime 23°5, magne- 
sia 16°5, manganese protoxide ‘3, iron protoxide 4°5=100. 
Fuses B.B., but its fusibility varies with the composition, 
anc the ferriferous varieties are most fusible. Insoluble in 
acids. 
Diff. Its crystalline form, and its ready cleavage in two 
planes nearly at right angles to one another, are the best 
characters for its determination. 
VARIETIES.—The varieties may be divided into three sec- 
