OF CORNWALL, 185 
Tin nearly approaches to Fiver in colour, but has fo much more its connex- 
fulphur in it, that it quickly tarn idles in the air or moifture, and is 1 v ° c "_ wlth fil * 
really not fo fubjedt to hold Fiver as its Ffter lead, which is reckon- 
ed an inferior metal ; but, beFdes the colour, it has feveral proper- 
ties in common with Fiver, and frequent connexions with it ; diflolved 
in ftrong acids it grows bitter as well as Fiver ; fufed with Fiver 
obftinately adheres to it, and reFfts lead almoft as much as Fiver. 
Silver, though not of the pureft kind, may be extracted from tin \ 
In the neighbourhood of Oruro (a town in Peru famous for the 
mines near it) is the Colloquiri, which although a mine of tin, yet 
now and then in following the veins thereof, they meet with rich 
ores of Fiver, which they call Lipta 
Native tin, or tin found in the Cornifh mines in a metallic Fate, Native tin. 
I am not certain that I ever faw; but March 21, 1747, viewing a 
rich piece of tin-ore from Boffehan in the parifh of St. Juft in a 
microfcope, I thought I faw a Fnall lift of maturated tin, white, 
fhining like a thread of melted pewter; I then took a greater mag- 
niFer, and plainly perceived the fame lift; but intending to try 
further experiments to afcertain the truth, I could not afterwards 
Fnd the fpecimen, and therefore do not aflert the matter of fadt. 
Agricola u aflerts, that this metal is no where found fo pure as to be 
malleable; but the learned Dr. Grew (Mufeum R. S. page 328) 
defcribes one fpecimen of “ native tin lying as it were in bright 
drops in a brown ftone,” and I fee no reafon yvhy tin may not pof- 
Fbly be reFned, and the impurities of its pabulum feparated by dif- 
folvent juices in the bowels of the earth, in like manner as copper 
is. Metals (as it feems to me) are only enftirined, more or lefs 
concealed, and wrapt up into ores by falts, fulphur, and ftone, 
which are fometimes removed by a fubtil menjlruum in the earth. 
This is frequently the caffe of copper, fometimes of Fiver; and gold, the 
moft perfedt of metals, is ftill more frequently found in a metallic than 
any other ftate ; but with tin this very rarely happens, by reafon of 
the fcarcity of its proper ?nenjlruum . Sea-falt (the baFs of aqua 
regia) being the only fait we know which will operate on tin, dif- 
perfe the impurities, and releafe the metal. 
As white as tin is when melted, yet in the ore it is generally Tin cryftais. 
black, and the cryftais, which inclofe the metal, are like black 
glafs. We have however fome white, fome cinereous, and fome 
red tin grains, and fome of a reFnous colour, but they are rare, 
and I fear often thrown away by the heedlefs, although curious as 
well as proFtable. Stamping and drejfing do but pulverize and 
reduce the ore to fmaller cryftais, and the fordes which intervene 
• See Boerh. Chem. by Shaw, page 97. u Page 421, fee alfo Woodward’s Cat. vol. I. 
' Alonfo Barba, page 92. clafs ii. part fecond. 
B b b being 
