Constituents of various Minerals. 267 



14. Green Carbonate of Strontian. 

 i 



It is well known to mineralogists, that, in the lead-mine of 

 Strontian in Argyleshire, two different varieties of carbonate of 

 strontian occur, the one green coloured, the other yellowish- 

 brown. But though these varieties have been long known, I am 

 not aware that they have hitherto been subjected to a chemical 

 examination, or that their true chemical constitution has been 

 determined. I had, indeed, analysed both several years ago ; but 

 the results of my investigation have hitherto lain by me unpub- 

 lished. Last summer, Mr THOMAS MUIR repeated the analysis 

 of both varieties with very great accuracy, and I shall here state 

 the result of his investigation. 



It is well known that the green variety has an asparagus- 

 green colour, and that it is composed of imperfect prisms, slight- 

 ly diverging from a common centre. The specific gravity is 

 3.713. The constituents are, 



Carbonate of Strontian, . . 93.493 



Carbonate of Lime, . . . 6.284 



Carbonate of Manganese, v trace. 



Oxide of Iron and Alumina, 0.010 



99.787 

 or almost exactly of 



1 atom carbonate of lime, 

 10 atoms carbonate of strontian. 



To what is the green colour of this mineral owing ? 



15. Brown Carbonate of Strontian. 

 This variety, judging from the number of specimens in my 



VOL. XI. PART II. Mm 



