MINERALOGY, 53 



M It is, when fresh, in masses of a scaly structure and 

 of a deep black colour, with a highly metallic lustre, much 

 resembling coarsely foliated graphite ; after a few months 

 it partly falls to powder, or rather into scaly flakes, evi- 

 dently from the decomposition of pyrites, of which it con- 

 tains three per cent. It powders easily, but the powder is 

 always scaly, soiling, greasy, and glittering, like graphite. 

 If the pulverised part be washed and ground, the tougher 

 metallic looking scales remain as a black micaceous resi- 

 duum, and it is oniy after long rubbing and washing that 

 they also are pulverised, showing great toughness in the 

 compacter and larger scales of the mineral. It soils much, 

 but is too soft to mark with, nor can any very determined 

 streak be made ; what is so, is of a deep black. When 

 heated a little sulphur sublimes ; the mass burns but very 

 slowly indeed, reddening only at first and for a long time 

 like some varieties of graphite, and requiring a good sup- 

 ply of air to the crucible and constant stirring to effect its 

 combustion. 



" With patient attention the whole is burnt, with the 

 exception of a small residuum of a very light, and bright 

 fawn-coloured powder, which is a mixture of oxide of iron 

 and silex. 



Its composition is found to be in 100 parts. 



Carbon, ••• ••• ••• ••• 85-70 



Water and sulphur, ••• ••• 400 



Peroxide iron, ••• ••• ■•• 250 



Earth, chiefly silica, ••• ••• 7-50 



99-70 

 Water and loss, ••• ••• •« 30 



100 00 

 1 This mineral then, differs from the anthracites in its 

 high lustre, scaly structure, and ready pulverisation, by 

 which it approaches the graphites ; as well as by its iron 

 and very slow combustion ; but then from these it differs 

 by its streak, and high combustibility with nitre; for, like 

 coal and the anthracites, when projected upon melted nitre it 

 deflagrates, heating the crucible instantly to redness, while 

 <he graphites not only boil but heat the crucible also, and 



G 



