Mineral Suhjlance from New South Wales. 
6f reducing it into fine powder arifing from a property of ano- 
ther kind, unttuofiry. 
The difference, above taken notice of, between this blade 
matter and common black-lead, confifts only in the former 
leaving on calcination a white fubftance, feemingly filiceons, 
and the latter a brown ferrugineous one. In their afped, 
tmftuofity, refiftance to acids, and the volatility (in open fire) 
of that part in which the blacknefs confifts, they perfectly 
agree; and they appear to agree alfo in the nature or conftitu- 
tion of this volatile part ; for the Sydney-Cove mineral, as 
well as black-lead, deflagrates and effervefces very ftrongly 
with nitre, produces an hepatic impregnation on fufion with 
vitriolated alkali, but none with pure alkali, and is manifeftly 
rich in inflammable matter, without fulphur. 
It feems, therefore, that this fubftance is a pure fpecies of 
plumbago, or black-lead, not taken notice of by any writer 
I have met with, Fourcroy, in the laft edition of his Che- 
miftry, looks upon iron as an effential component part of 
black-lead, to which, accordingly, he gives a new name ex- 
preffive of that metal, cdrbure de fer. Lavoisier, in his 
Elements of Chemiftry, lately publifhed, mentions a carbure 
of zinc alfo, and fays that both thefe carbures are called plum- 
bago, or black-lead. The quantity of mineral I had been fur- 
nifhed with was too far exhaufted, before I met with this ob- 
fervation, to admit of any further experiments, for determining 
the prefence of zinc in it ; but thofe already ftated, with the 
recolle£lion of fome circumftances attending them, perfuade 
me, that that metallic body has no Ihare in its compofition. 
Neither before the blow-pipe, nor in calcination, was there 
any appearance of the peculiar flame, or flowers, by which 
zinc 
