112 



schaller: alunite-beudantite group 



Comparison of Analysis with Calculated Values 



The figures prove, I believe, that the composition of the min- 

 eral nephelite can be solved by the explanation herein offered 

 which rests primarily on the isomorphous relation of (Si0 4 ) and 



(Si 3 Os). 



The remarkable fact that the compound KAlSi0 4 is always 

 present in nephelite to the extent of about 20 per cent has as yet 

 not received any adequate explanation. 



MINERALOGY. — The alunite — beudantite group. Waldemar 

 T. Schaller, Geological Survey. To appear in the American 

 Journal of Science. 



A consideration of the various possible members of the alunite- 



beudantite group has led to some interesting results for fuller 

 description of which reference must be made to the complete 

 paper. Hamlinite is doubtless identical with goyazite; utahite, 

 cyprusite, raimondite, pastreite, carphosiderite and apatelite 

 are probably all the same mineral with the formula H 2 0.3Fe 2 3 . 

 4S0 3 .6H 2 0; and the probable compositions of pharmacosiderite 

 and harttite are suggested. All of the minerals of these groups 

 have very similar crystallographical and optical properties. 

 Their formulas may be so written as to clearly bring out their 

 close chemical relationship. The minerals may be placed into three 

 sub-groups which are: sulphates, phosphates, and sulphate- 

 phosphates respectively; the general formula for each of these sub- 



