370 Dr. Thomas Thomson on some new [May 



the baryto-calcite of Brooke, and the stromnite of Dr. Trail, 

 together with harmotome and brewsterite, we enumerate 

 almost all the species of minerals containing barytes at 

 present known. Having, during an examination of the 

 mineral kingdom, in which I have been occupied for the 

 last eight years, met with several other minerals containing 

 barytes, and differing specifically from those already known, 

 it may, perhaps, be acceptable to mineralogists if I give a 

 short account of the most remarkable of those in this place. 

 1. Calcareo- Sulphate of Barytes. — This species, though 

 hitherto overlooked by mineralogists, occurs rather abun- 

 dantly in the lead mine of Strontian. This mine, as has 

 been long known, constitutes a vein in a mountain, con- 

 sisting partly of granite and partly of gneiss, and the vein 

 divides the granite portion from the gneiss. The gangue of 

 this vein consists of carbonate of lime, carbonate of stron- 

 tian (towards the bottom,) sulphate of barytes, harmotome, 

 calcareo-sulphate of barytes, &c. This last mineral pro- 

 bably has been overlooked, because it never occurs in the 

 state of crystals. 



Colour, snow white; texture, foliated; very frangible; 

 translucent on the edges. 



Hardness, 2- 75 on Mohs's scale; specific gravity 4*1907. 

 Before the blowpipe decrepitates, but does not fuse. When 

 subjected to analysis I obtained the following constituents : 



atoms. 



Barytes i . . 48*945 - 



Strontian . . 0*790 - 



Lime .... 6*605 - 



Sulphuric-acid . 35*230 - 



Silica. ... 4*140 - 



Alumina . . . 3*460 - 



Protoxide of iron 0*450 - 



Moisture * * 0*565 



100*185 

 We see that the sulphuric acid almost exactly saturates 

 the barytes, strontian, and lime. From this it can scarcely 

 be doubted that the other constituents are merely acciden- 

 tally present, and do not constitute an essential part of the 

 mineral. 



