296 CELESTINE AND BARYTO-CELESTI NE OF CLIFTON. 



isomorphoQS mixture. I also determined the sulphuric acid. 



1.3245 grms. of the mineral gave 1.46, BaSOi = 38.5 per 

 cent. Sulphuric Acid. 

 Theory for formula, 2 BaS04, SrS04 ... 37.0 % 



The matrix was only slightly soluble in acids, but (m fusing it 

 with sodium carbonate, a brisk effervescence occurred. On 

 cooling, the mass was of a bright green colour, thus proving that 

 manganese was present. I also found silica, alumina, and traces 

 of iron and calcium. 



Baryto-celestine seems to have been found only in three other 

 localities. At Kingstown and Lake Erie in Canada a mineral of 

 the composition 2 SrSO^, BaSOi, has been obtained according 

 to Thomson. This statement has, however, been contradicted by 

 some writers who assert it to be pure celestine. 



At Binnenthal in Switzerland, baryto-celestine occurs composed 

 of 87.8 barium sulphate, and 9.1 strontium sulphate, and in 

 Hanover a mineral named greimerite is said to have been found 

 consisting of barium and strontium sulphates, but the proportions 

 are not mentioned. 



Allied to this is a mineral from the chalk marls of Moen, 

 containing barium, strontium, and calcium sulphates, calcium 

 carbonate and water. 



As regards the crystalline form of my specimen, Mr. Sollas who 

 very kindly examined it, states that the angles appear to be 

 identical with those of pure celestine. 



The appearance of the crystals when examined under the 

 microscope is remarkable ; the fundamental form is that of an 

 elongated octagonal plate the edges of which are truncated. 



In some of the crystals the edges at the extremities are serrated, 

 occasionally too, minute rosettes occur in the crystals, and cavities 

 were found, the walls of which were also serrated. The specific 

 gravity of the mineral was determined both by weighing a lump 

 alone, and in water, and also by weighing the powder in a specific 



