418 KEPORT OF NATIONAL MUSEUM, 1899. 



■statod bv Dana to occur in large quantities at Smoky Mountain, in 

 North Carolina, and large quantities of an impure variety, often of a 

 yellowish cast, are found in Grant County, on the Gila River, about 40 

 miles north of Silver City, New Mexico. (Specimen No. 07841, 

 U.S.N.M.) The mineral is also found in Ci'ooke and Fremont counties, 

 Wyoming (Specimen No. 6ii087, U.S.N.M.); in Schemnitz, Hungary 

 (Specimen No. 53047, U.S.N.M.), and in Japan (Specimen No. 34402, 

 U.S.N.M.). 



The chief use of the material, were it procurable cheaply and in 

 quantities, would he as a source of alumina for use in chemical manu- 

 facture and as an ore of aluminum. » 



Concerning the occurrence of alunogen on the Gila River, New 

 Mexico, W. P. Blake writes: 



In a region about half a mile square, of nearly horizontal strata of volcanic origin, 

 there has been extensive alterati(jn and change by solfataric action, or possibly by the 

 decomposition of disseminated pyrites producing alumin(uis solutions, which, flowing 

 slowly by capillary movement from within outwards, suffer decomposition at the sur- 

 face with the production of sulphate of alumina (alunogen) in crusts and layers upon 

 the outer portions of the rocks, attended by the deposition of siliceous crusts and the 

 separation of ferric sulphate, while the rocks so traversed appear to be deprived of a 

 part, at least, of their silica and of their alkalies, with the formation of liauxite. 



The alunogen is thus an outer deposit, while the l)auxite is not a deposit, but is an 

 internal residual mass in place. Its t-olor is generally ])luish-white; structure, amor- 

 phous, granular, without concentric or pisolitic grains. When dried in the sun and 

 air it will still lose about 20 per cent by ignition. It gives only about 1 per cent of 

 soluble matter by leaching with water; is infusible, and reacts for alumina. The 

 amount of residual silica and alkalies has not yet been ascertained, and no careful 

 full analysis has been made. The composition is no doubt variable in samples from 

 different places, for the original rocks give evidence of a great difference within short 

 distances. ' 



Material from this locality (represented by Specimen No. 67841, 

 U.S.N.M.) analyzed in the laboratories of the United States Geolog- 

 ical Surve}^ yielded results as below: ^ 



Alumina {AU%) 15. 52 



Sulphur trioxide (SO3) 34. 43 



Water (H^O) 42. 56 



Insoluble residue - 7. 62 



100. 1;} 



An asbestiform hulotrichite from the same locality yielded — 



Aluuiina ( AlA) ''•27 



Iron protoxide (FeO) 13.59 



Sulphur trioxide (SO3) 37. 19 



Water 40.62 



Insoluble residue 0. 50 



99.17 



' Transactions of the American Institute of Mining Engineers, XXIY, 1894, p. 

 572. 



^American Journal of Science, XXVIII, 1884, p. 24. 



