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Diamond. 
The diamond is the purest form of carbon, the colourless varieties leaving but 
a trace of ash, whilst the coloured ones leave from 0’2 to 0*6 per cent. 
They are found as crystals mostly in alluvial deposits, but in one or two 
places they have been found in the matrix. 
The colour varies from colourless to yellow, red, orange, green, blue, brown to 
black, with a brilliant lustre, transparent, with the exception of the dark varieties, 
which are translucent. When rubbed they become electric, and some possess a 
certain amount of phosphoresenee. Colourless diamonds are of great value, owing 
to their hardness and brilliancy, but all the other colours are valuable, even the 
black, which is used for boring purposes. 
Graphite, Plumbago, or Black Lead. 
This is usually found foliated, massive, or granular, of a lead-black colour 
with a metallic lustre. Its hardness is from 1 to 2, and specific gravity about 
‘^'25. It will mark paper, and feels greasy to the touch. It consists of about 95 
to 99 per cent, of carbon, is infusible both alone and with re-agents, and is not 
affected by acid. It is found amongst the crystalline rocks of this Colony in small 
quantities, but mostly in a very impure state, as at Kendinup, the Lower Blackwood, 
and Northampton District. 
Mineral Coal 
Is massive, of a brown or black colour, opaque, brittle, or imperfectly sectile, 
having a hardness of from 0'5 to 2'5, and specific gravity of from 1*2 to 1'8. 
It is composed of carbon, with some oxygen, hydrogen, traces of nitrogen, 
water, and earth minerals. 
Anthracite .—Glance coal or stone coal.—Is a hard, black, compact variety, 
with a high lustre, and is often iridescent. Its specific gravity is from 1 3 to 173, 
containing from 80 to 93 per cent, of carbon, and from 4 to 7 of volatile matter, 
and a little earthy matter. It ignites with difficulty and burns with a feeble blue 
fiame. It is largely used for steam purposes, where a great body of beat is 
squired without much smoke and gas. 
Bituminous Coals .—This coal is black in colour, but softer, and not so 
brilliant as anthracite, with a specific gravity not over 1*5. There is a great 
variety in the coals of this class, in the amount of oil, coal-tar, or gas they yield. 
T-bey are divided into caking and non-caking coals; the former, when heated, 
softens, and burns with a yellow-smoking flame, requiring a great deal of stirring 
lo prevent the fire clogging up, whilst the latter, although they resemble the 
former in appearance, do not soften but burn away freely to an ash. The chemical 
difference of these two coals is not. understood. 
Cannel Coal— This is a very compact, even textured, dull coal, which breaks 
w dh a large conchoidal fracture. It burns readily with a yellow fume without 
citing, so that pieces of it can be used as candles, from which it derives i s 
faille. It contains as much as 50 to 60 per cent, of volatile matter, and thereloie 
18 birgely used in the manufacture of gas. 
Brown Coal. — This is usually of a brownish-black colour, but sometimes 
Resembles bituminous coals so closely that it is impossible to distmgujs i iem - 
I be term has been applied to all coals of a move recent age than those o ie gica 
coalfields of the world. The name lignite is sometimes used m the same sense, 
ait it is not strictly correct, except when the coal shows woody struc uic. 
Jet .—This belongs to the same class and resembles cannel coal vov ^sely bi 
appearance, but is much harder and of rather a deeper colour. It is capable ot 
receiving a brilliant polish, so is used in jewellery. 
