RE-EXAMINATION OF AMERICAN MINERALS. 149 



bury. It occurs at a place called Alum Point, and was con- 

 sidered altogether a manganese alum, of which Dr. Gale gave 

 what he then stated he considered an imperfect analysis (Amer- 

 ican Journal of Science and Arts, vol. xv, 2d series, 434) : 

 S 18.0 Mn 8.9 SI 4.0 H 73.0 



Being desirous of having it more carefully analyzed, Dr. 

 Gale placed in my hands the specimen which is the subject 

 of the present investigation. It was not received as it occurs 

 at the locality, but had been recrystallized, and consisted of 

 delicate needle-shaped crystals, adhering in small masses. It 

 dissolves very readily in water ; in fact so soluble is it that 

 it is difficult to decide the amount of water requisite for its 

 complete solution. It crystallizes from solution in the form 

 of delicate crystals, with a plumose aggregation. On analysis 

 it furnished : 



Alumina 10.40 10.65 



Magnesia , 5.94 5.65 



Manganese 2.12 2.41 



Sulphuric acid 35.85 35.92 



Oxide of iron .15 .09 



Potash 20 .20 



Water 46.00 46.75 



100.66 101.67 



This analysis shows an amount of protoxides a little too 

 high for the requisites of the formula of alum ; but this, how- 

 ever, is of frequent occurrence in the natural alums, owing to 

 admixture of impurities. This variety of alum has been be- 

 fore observed by Stromeyer, and was brought from a cave in 

 Southern Africa. Its formula is (Mg, Mn) s+£l"S 3 +24H. 



44. Apophyllite. 



The specimen of this mineral examined came from Lake 



Superior. It is eminently lamellar in its structure, and was 



placed in my hands as being possibly diaspore ; its luster is, 



however, much more pearly than this latter mineral. Its 



specific gravity is 2.37 and its constitution 



Silica 52.08 



Lime 25.30 



Potash 4.93 



Fluor 96 



Water 15.92 



99.19 

 11 



