284 Elements of Mineralogy. 



is volatil, in a ftrong heat long continued, 

 and feems to contain iron, plumbago, and 

 coal intimately mixed. The other burns 

 with a languid flame, lofes about 4. of its 

 weight, refembles pit-coal, but is fomewhat 

 harder, and yields about 30 per cent of iron. 



SPECIES XXII. 

 Mineralized by the Vitriolic Acid. 



36. This has been mentioned under the 

 head of faline fubftances. 



Uncertain Mineralizations. 



SPECIES XXIII. 



Iron Blende. 



37. TThls is faid by Mr. Monhet to be a 

 ftone of a grey iron colour, formed of di- 

 verging laminae, of great hafdnefs and a 

 metallic appearance, but infoluble in acids, 

 and infufible in the ftrongeft fire, Mineral. 

 356. Sometimes this ftone contains arfenic, 

 in this cafe it blackens by expofure to the 

 air. 



SPECIES XXIV. 



Wolfram. 



38. This flone which is generally found 

 in tin mines, is of a black or brown fhining 



colour, 



