MINERALOGY. i8t 
corroded into a white powder by the fpirlt 
of nitre. 
The vegetable acid, foaps, and pure alca- 
line falts, alfo corrode this metal by degrees. 
/. Its fpecific gravity to water is as 7400 to 
1000, or as 7321 to 1000. 
m. DifTolved in aqua regia, which for this 
purpofe ought to confift of equal parts of 
the fpirit of nitre and fea-falt, it heightens 
the colour of the cochineal, and makes it 
■deeper *, for otherwife that dye would be 
violet. 
SECT. CLXXXL 
Tin is not found naturally in the earth 
in any odher ftate than, 
I. In form of a calx. Stannum calciforme, 
A. Indurated, or vitrified, Induratum, 
I. Mixed with a little of the calx of 
arfenic, Minera ftanni vitrea arfe- 
ni calls, 
a. Solid tin ore, without any deter- 
minate figure, Tin-f^one. 
It refembles a garnet of a 
blackifh brown colour, but is a 
great deal heavier ; and has been 
confjdered at the Englifh tin- 
mines as a ftone, containing no 
metal, until fome years ago it 
began to be fmeited to great ad- 
vantag-e. 
O ^ 
h, Criflallifed, Cryftaliifatum^ Tin- 
grains. 
Is like the garnets, of a fphe- 
rical polygonal figure, but looks 
more unduous on the fnrface. 
N 3 I. In 
