UNISILICATES. aoe 
Color deep red to cinnamon color; also brown, black, 
green, emerald-green, white. a to opaque. Lus- 
fre vitreous. Brittle. H.=65-7°5. G.—3-1-4:3. 

Composition and Varieties. The general formula for the 
species is (R38). O1. Si3; in which R may be calcium, mag- 
nesium, iron, manganese, and R may be aluminum, iron, 
chromium, ‘The varieties owe their differences to the pro- 
portions of these elements, or the substitution of one for 
another. Most garnets fuse easily to a brown or black glass ; 
_ but the fusibility varies with the constituents, and chrome- 
garnet is infusible. They are not decomposed by hydro- 
chloric acid ; but if first ignited, then pulverized and treated 
with acid, they are decomposed, and the solution usually 
gelatinizes when evaporated. 
There are three series among the varieties : one, that of 
alumina-garnet, in which the sesquioxide base is chiefly 
alumifium ; the second, that of iron-garnet, in which the 
sesquioxide base is chiefly iron instead of aluminum ; and 
third, chrome-garnet, in which it is chromium. 
J. ALUMINA-GARNET. 
Almandite (Almandine). An iron alumina-garnet, Fe, 
Al O,.Siz=Silica 36° IL alumina 20°6, iron protoxide 43:3 = 
100. It occurs’ of various shades of red from ruby-red and 
hyacinth-red, to columbine-red and brownish red. When 
transparent it is called precious garnet; and, if not so, 
common garnet. 
Grossularite (including Cinnamon Stone). <A lime alu- 
mina-garnet, Ca; Al O,,Si,=Silica 40°1, alumina 22°7, lime 
87°2=100, but often with some iron protoxide in place of 
part of the lime. The name Grossularite was given to a 
pale-green garnet, in allusion to the color, from the Latin 
name for gooseberry. Cinnamon Stone includes the cinna- 
mon-colored yaricty. 
