Dr. Thomson on tome New Minerats. 66 



99-8 

 Its constitution may be represented by the formula, 14 (MgS) 

 + 3(1/4- iAl)S' +11 Aq. 



Asbostus contains more silica, and a good deal of lime, which is 

 wanting in baltimorite. Asbestus, in fact, is merely a variety of 

 pyroxene. 



7. For the next mineral, which, from its constitution, I call snhses- 

 quisulphate ofaluminay I am also indebted to Mr. Alger. The locality 

 is South Peru. 



It is a soft opaque mineral, composed of silky fibres adhering to 

 each other. The colour is white, but there is a reddish-yellow tint 

 which partially pervades the specimens, owing, obviously, to a little 

 foreign matter with which they are stained. The taste is acid and 

 sweet, like that of alum. The specific gravity is 1*584. It is soluble 

 in water. The constituents are 



Sulphuric acid, . . 32-95 

 Alumina, ' . . . 22-55 

 Sulphate of soda, . . 6*50 



Water 3920 



101-2 



obviously 



1 atom sulphuric acid, . 5 



1 J atom alumina, . 3*375 



1 atom sulphate of soda, . 9*0 



5 atoms water, . . 5-625 



23 



The sulphate of soda exists in a greater proportion than sulphate of 

 potash or of ammonia does in our alum. It is curious that in South 

 America, soda almost universally replaces the potash which occurs in 

 other parts of the world. Instead of saltpetre, so abundant in India, 

 and even in Europe, we have nitrate of soda in Peru ; and, instead of 

 potash alum, we find, in Buenos Ayres, and other districts of South 

 America, soda alum, deposited in amygdaloidal cavities in a kind of 

 shale. 



8. Messrs. Alger and Jackson gave the name of acadialite to a 

 variety of chabasite which they found in Nova Scotia, and specimens 



