242 J. B. Mackintosh — Iron Sulphates from Chili. 



Art. XXXYI. — Notes on some Native Iron Sulphates from 

 Chili;* by James B. Mackintosh. 



In March, 1887, I received from Dr. Thos. Egleston a 

 series of the native iron sulphates from South America, which 

 I analyzed for him, as there were some minerals among them 

 which he was not able to identify and which he regarded as 

 probably new. It is with his permission that I now give 

 the results of my analyses and the conclusions to which they 

 lead. My results confirm his opinion as to the novelty of 

 some of the specimens analyzed. 



Among the series of specimens were several of well known 

 species, of which I also made analyses. These I will give first, 

 with but little comment, as they do not afford much that is 

 new, and then take up the new varieties in turn. 



1. Coquimbite. — Of this species I had three varieties, as de- 

 scribed below, which gave the following results : 



I (No. 1). II (No. 2). Ill (No. 10). 



Amethystine Amethystine White 



crystalline massive massive 



transparent. translucent. opaque. 



Specific gravity.. 2-07 2-086 



S0 3 43-40 42-90 42-32 



Fe 2 3 22-17 26-10 28'10 



A1 2 3 439 1-65 |^5 J 0-91 



Na 2 0-25 0-27 3 



„ >. I traces traces 



MgO [ 



H 2 (difference) . [29-79] [29-08] [28-67] 



All lead to the same formula, Fe 2 3 , 3S0 3 , 9H 2 0. The 

 water expelled at 110° in the three samples was 5, 6, and 5-J 

 molecules respectively. It is interesting to notice that the most 

 crystallized and transparent specimen is the poorest in iron and 

 richest in alumina, while the most opaque and non-crystallized 

 is the richest in iron. 



2. Copiapite (No. 6). — The specimen analyzed was massive, 

 yellow, with specific gravity = 2'118. The analysis gave 



SO s 39-03 



Fe 2 3 29-16 



FeO 1-56 



Na 2 0-31 



H 2 [29-94] 



* Recent contributions to our knowledge of the iron sulphates of South America 

 have been given by Frenzel, on amarantite and hohmannite, Min. petr. Mitth., 

 ix, 397, 1887 ; and by G. Linck on coquimbite, copiapite, quenstedtite, stypticite, 

 roemerite, halotrichite,. 4 Zeitschr. f. Kryst, xv, 1, 1888. 



