114 Account of a Discovery of Native Minium. ; 
indirectly it is true ; and lastly, that M1. Proust probably did - 
_not make use of pure acetates in his labours, or that the ethe- 
real pungent empyreumatic smell made him conjecture that 
there was ammonia present. 
KXII. Account of a Discovery of Native Minium. In & 
Letter from James Smiruson, Esq. F.R.S., to the 
Right Honourable. Sir JoserH Banks, K. 5, P.R.S.* 
MY DEAR SIR, 
T BEG leave to acquaint you with a discovery which I have 
lately made, as it adds a new, and perhaps it may be thought 
an interesting species, to the ores of lead. I have found 
minium native in the earth. 
_ It-is disseminated in small quantity m the substance of 
a compact carbonate of zine. 
Its appearance in general is that of a matter in a pulveru- 
lent state, but in places it shows to a lens a flaky and cry- 
stalline texture. , 
Its colour is hike that of a factitious minium, a vivid red 
with acast of yellow. 
Gently heated at the blowpipe it assumes a darker colour, 
but on cooling it returns to its original red.” At a stronger 
heat it melts to litharge. On the charcoal it reduces to lead. 
Tn dilute white acid’ of nitre it becomes of a coffee colour. 
On the addition of a little sugar, this brown ealx dissolves, 
and produces a colourless solution. 
By putting it into marine acid with a little leaf gold, the 
gold is soon entirely dissolved. 
When. it is inclosed in a small bottle with marine acid, 
and alittle bit of paper tinged by ternsole is fixed’ to the 
cork, the paper in a short time entirely loses its blue colour, 
and becomes white. A strip of common blue paper, whose 
colouring matter is indigo, placed in the same situation, 
undergoes the samme change. 
The very small quantity which I possess of this ore, andi 
* From the Transactions of the Royal Suciety for 1806, : ’ 
‘a 
