1835. J Species of Minerals containing Barytes. 373 



Its constituents, as determined by Mr. Richardson in my 

 laboratory, are, 



Carbonate of barytes . . 

 Carbonate of lime . . . 

 Sulphate of barytes . . 

 Peroxide of iron . . . 

 Water, or volatile matter 



98-15 

 It is obviously a compound of 



1 atom carbonate of barytes. 

 1 atom carbonate of lime 

 Sp. 5. Bicalcareo- Carbonate of Barytes. — This mineral was 

 (among others) exposed for sale in Glasgow in November 

 1834, by Mr. Cowper, a mineral dealer from Alsten Muir. 



1 purchased a specimen, and subjected it to chemical ana- 

 lysis, because it appeared to be new. Colour, snow white. 



Crystallized in beautiful dodecahedrons with triangular 

 faces, composed of two six-sided pyramids applied base to 

 base. The faces were not bright enough to admit of mea- 

 suring their inclinations to each other. The inclination of 

 a face of one pyramid to the corresponding face of the other 

 was about 132° and the angles of the plane separating the 

 two pyramids were about 120°. Only a single cleavage 

 could be observed. 



The crystals were in groups, upon a white crystallized 

 substance, which I did not analyze, but it had the aspect 

 of sulphate of barytes. 



Lustre, vitreous ; cross fracture, uneven ; some imperfect 

 appearance of a foliated structure ; translucent ; hardness 

 2-25. Specific gravity 3-718. 



When dissolved in nitric acid it left 0*75 per cent, of 

 sulphate of barytes. The moisture, which rather exceeded 



2 per cent., was doubtless hygrometrical. Abstracting 

 these bodies, which I considered as foreign, the constituents 

 were atoms. 



Carbonate of barytes . . . 49-31 or 4*02 

 Carbonate of lime .... 50-69 „ 8-01 



100- 



