320 DESCRIPTIONS OF MINERALS. 



strong pearly and brilliant, of sides of crystals vitreous. 

 H.=3 -5-4-5. G.=2.99. 



Composition. H 2 RA1 2 12 Si,= Silica 30*1. alumina 51.2, 

 lime 11-6, soda 2-6, water 4*5=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, X. C; at Chester, Mass. Named from the Greek 

 m argarites, a pearl. 



Willcoxite is near margarite. Dv.dleyite is an alteration product of 

 margarite. 



Chloritoid.— Masonite. Phyllite. Ottrelite. 



Monoclinic or triclinia Cleavage basal, perfect. Also 

 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 6 Si + l aq = Silica 24*0, alumina 40*5, 

 iron protoxide 28 4, water 7*1 = 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 Asia 

 Minor, with emery ; at St. Marcel ; Ottrez/ France (Ottre- 

 lite) ; Chester, Mass.; in Bhode Island (Masonite) ; at 

 Brome and Leeds, Canada. Phyllite in scales character- 

 izes the "spangled mica slate'"' of Xewport, B. I., and 

 Sterling, Goshen, etc., Mass. 



Seybertite. Occurs in somewhat mica like, or thin foliated forms, 

 with perfect basal cleavage, and laminae brittle, the color reddish or 

 yellowish brown to copper-red. Analysis by Brush obtained Silica 20 24, 

 alumina 39 "13, iron sesquioxide 3*27, magnesia 20*84, lime 13*69, water 

 l - 04, potash and soda l - 43, zirconia 0*T5 = 100"39, giving the quantiva- 

 lent ratio for protoxides, sesquioxides, silica, and water 6 : 9 : 5 : £. From 

 Amity, X. Y. ; Slatoust, Urals {XanthopJiyllite) ; Fassa Valley (Bran- 

 disite and Disterrite). 



IV. EYDKOCAHBOX COMPOUNDS. 



The following are the subdivisions here used. 

 I. Simple Hydrocarbons : Marsh-gas, Mineral oils, and 

 Mineral wax. 



