9 2 Elements of Mineralogy. 



ed ; 5 th ' fufibility per fe> as it is faid, though 

 I could not melt it with the blow-pipe. It is 

 frequently mixed with pyrites. 



I. VARIETY. 



Black Horn-ftone, Corneus Nitens Waller, 

 Sp. 169. 



Its texture is lamellar or granular ; the for- 

 mer is fometim^s fo foft as to be fcrapedvwith 

 the nail ; its furface frequently as glofTy as if 

 it had been greafed : its fpecific gravity is from 

 3, 6 to 3,88; it poflefles befides all the fpecific 

 properties above- mentioned in a high degree : 

 it does not detonate with nitre : it becomes 

 of a fnuff colour when heated, and then 

 flightly effervefces with diluted nitrous acid : 

 its folution in this acid is of a greenifh colour. 



In order to difcover the principle on which 

 its fmell depends, I boiled its powder in wa- 

 ter, but did not find the water altered in tafte, 

 nor did any teft I applied ihew any change 

 in it. 



I found TOO gr. of the lamellar fort to con- 

 tain 37 of filex, 22 or argill, 16 of magne- 

 fia, 2 of calcareous Earth, (both in a mild 

 ftate and 23 of calx of iron, not much de- 

 phlogifticated. 



II. VARIETY, 



