MINERALS OF CHILE. 71 



a sulphur-yellow. It has the same luster as the chloride ; it 



is, however, harder than the latter; its specific gravity is the 



same as the bromide. The composition of it is 



Silver 66.96 



Chlorine 13.20 



Bromine 19.84 



Formula is Ag (CI Br). 100 - 00 



IODIC SILVER. 



This beautiful and rare mineral has been found in some 

 little quantity in the silver-mines of Algodones, province of 

 Coquimbo. The mineral is of a pale sulphur-yellow color, 

 very fragile and soft, having a specific gravity of 5.5. One 

 specimen that I saw had crystalline faces, indicative of a 

 rhombic dodecahedron. It is commonly lamellar, and M. Do- 

 meyko has recognized in some small pieces three rhomboidal 

 cleavages ; two of the cleavages appear quite perfect, having a 

 pearly luster. It is more brittle and more fusible than either 

 the chloride or the chloro-bromide. The presence of iodine 

 and silver are readily recognized by the ordinary tests. Its 

 gangue is composed partly of carbonate of lime and partly of 

 a brick-red fine clay. In the Carmen mine a considerable 

 amount of iodide was found in the first part of the vein ; at 

 the depth of twelve varas (thirty-three feet) it disappeared, 

 and chloro-bromide made its appearance in identically the 

 same gangue; and at a still greater depth the latter mineral 

 disappeared, and was replaced by the chloride, accompanied 

 with the sulphuret of silver. It has also been found in small 

 quantities at one of the mines of the Chanarcillo district. 



This interesting mineral has the same atomic constitution 

 as the other natural haloid salts of silver, as originally shown 

 by M. Domeyko ; although, in referring to certain works on 

 mineralogy, Domeyko is quoted as giving for its composition 

 one atom of silver and two of iodine, while the chloride and 

 bromide of silver are alluded to as constituted of atom and 

 atom, forgetting that the I 2 used (as is frequently done) corre- 

 sponds to I commonly used by American and English chemists, 

 making the formula as given by Domeyko Ag. I, which formula 

 is sustained by my analyses, as well as those made by M. 

 Domeyko. 



