COMPOUNDS OF ALUMINUM. 



197 



Diff. Near beryl, but distinct in not being regularly hex- 

 agonal in crystallization. 



*" Obs. Chrysoberyl occurs in the United States in granite 

 at Haddam, Conn., and Greenfield, near Saratoga, N. Y., 

 associated with beryl, garnet, etc. ; in Norway, Maine. 



The name chrysoberyl is from the Greek chrysos, golden, 

 and beryllos, beryl. 



The crystals are seldom sufficiently pellucid and clear 

 from flaws to be valued in jewelry ; but when of fine qual- 

 ity, it forms a beautiful gem, and is often opalescent. 



Fluorides of Aluminum. 



Cryolite. In snow-white masses, having rectangular cleavages, and 

 remarkable for melting easily in the flame of a candle, to which its 

 name (from the Greek kruos, ice) alludes. H.=2 5. G. =2*95. It is 

 a sodium-aluminum fluoride. From Greenland. 



Chiolite and Chodneffite are near cryolite in composition and charac- 

 ters. Arksutite, Gearksutite, Pachnolite, Thomsenolite are related fluor- 

 ine compounds which occur associated with the Greenland cryolite. 

 From Siberia. 



Fluellite. From Cornwall, in minute white rhombic octahedrons. 

 Contains fluorine and aluminum. 



Alunogen. — Hydrous Aluminum Sulphate. 



In silky efflorescences, and crusts of a white color, having 

 a taste like common alum. H. —1-5-2. G. =1*6-1 *8. 



Composition. Al 12 S 3 + 18aq = Sulphur trioxide 36*0, 

 alumina 15*4, water 48-6 = 100. 



Obs. A common efflorescence in solfataras of volcanic 

 regions, and also often occurring in shales of coal regions 

 and other rocks containing pyrite ; the oxidation of the 

 pyrite — an iron sulphide — affords sulphuric acid, which 

 acid combines with the alumina of the shale. 



