76 
CONTRIBUTIONS TO CHEMISTRY AND MINERALOGY. [bull. 167. 
Of the water, 10 percent escaped in twenty-four hours over sulphuric 
acid and only 0.4 per cent more in another like period, but a total of 
14.4 per cent after ten days' uninterrupted exposure. The water thus 
lost is very slightly reabsorbed on exposure to air. 
From calculations by Prof. F. W. Clarke the substance may be 
regarded as a mixture of alunogen or the halotrichite group, with 
salts of the melaiiterite group, the empirical formula being nearly 
(Fe. Mn) 4 (Zn, Mg) 2 Al 2 (S0 4 ), . 65H 2 0. 
The outer white zone of the specimen contained only 39.62 per cent 
of water. 
The second sulphate examined was a beautiful sky-blue stalactite 
from the Anaconda mine at Butte, collected by Mr. G. W. Tower. Its 
composition was as follows : 
The stalactite was of some size, and was most readily soluble in coJd 
water, the solution giving a strong acid reaction. The calculated ratio 
is strongly acid, showing either a mixture of highly acid salts or of 
normal salts with free acids. 
