320 DESCRIPTIONS OF MINERALS. 
strong pearly and brilliant, of sides of crystals vitrecus. 
Ws 545. Ge = 299. 
Composition. H,RAI, O.S8i,=Silica 30°71, alumina 51.2, 
lime 11°6, soda 2°6, water 45=100. B.B. whitens and fuses 
on the edges. 
Obs. Often associated with corundum and diaspore. Oc- 
curs in Asia Minor; at Sterzing in the Tyrol; in the 
Urals ; in Village Green, and Unionville, Pa:; in Buncombe 
County, N. C.; at Chester, Mass. Named from the Greek 
margarites, a pearl. 
Willcovite is near margarite. Dudicyite is an alteration product of 
margarite. 
Chloritoid.— Masonite. Phyllite. Ottrelite. 
Monoclinic or triclinic. Cleavage basal, perfect. Alsa 
coarse foliated massive; and in thin disseminated scales 
(phyllite or ottrelite). Brittle. 
Color dark gray, greenish, to black. Lustre of cleavage 
surface somewhat pearly. 
Composition. FeAl O,8i+1 aq=Silica 24:0, alumina 40°5, 
iron protoxide 28 4, water 71=100. B.B. becomes darker 
and magnetic, but fuses with difficulty. Decomposed com- 
pletely by sulphuric acid. 
Obs. Found at Kossoibrod, Urals, with cyanite ; in Asij 
Minor, with emery; at St. Marcel ; Ottrez, France (Ottre- 
lite) ; Chester, Mass.; in Rhode Island (Masonite); at 
Brome and Leeds, Canada. Phyllite in scales character- 
izes the “spangled mica slate” of Newport, KR. I., and 
Sterling, Goshen, ete., Mass. 
Scybertite. Occurs in scmewhat mica like, or thin foliated forms, 
with perfect basal cleavage, and lamine brittle, the color reddish or 
yellowish brown to copper-red. Analysis by Brush obtained Silica 20°24, 
alumina £9°13, iron sesquioxide 3°27, magnesia 20°84, lime 13°69, water 
1:04, potash and soda 1:48, zirconia 0°75=100°39, giving the quantiva- 
lent ratio for protoxides, sesquioxides, silica, and water 6 :9:5: 5. From 
Amity, N. Y.; Slatoust, Urals (Xanthophyllite) ; Passa Valley (Dran- 
disite and Disterrite). 
IV. HYDRCCARBON COMPOUNDS. 
The following are the subdivisions here used. 
I. Srupte Hyprocarpons : Marsh-gas, Mineral oils, and 
Mineral wax. « 
