s e c t . nr.
Mines of
lead in Com
wall.
SECT. IV.
Sorts of
lead -ores.
210 N A T U R A L H L S T O R Y
io o o , or as c b i f id e s , >kati>wili diffolve in ®fcids,
but tin, like gold, in aqua regia only* Leadtherefore and tin are
two metals radically diftinâ:, each conftmt tptits- own peculiar
cific weight, and requiring a ^^Qxeritnienjlruum from the other.
Lead is of great ufe* not only in iheets, .pipes, or more folid.fiib-
ftances, but for refining other, metals, for making paints, varnifhing
potteryrware, for yielding oils, tinctures, and- fome other afliftances
in phyfic; lead will alfo yield filver, and fomekad. a quantity very
profitable to the owner.
O f this metal many mines have been .anciently and lately worked
in Cornwall', and in many places it is .difcovered among other
rnrtals but in too finall quantities to yield much profit. The mines at
Penrofe, nearHelfton, have been wrought above two hundred years,
and have yielded tolerable profit within 1‘hefe thirty, years ; >ffie ore
is moldy, o f that fort called Potter’s ore, but Jometimes. - yellow \
Dr. Woodward (Vol. II. page 29.) gives a very advantageous character
o f the ore found at Guamek, in,.îhe. parifo^fe &L Allen*
near Truro. “ It was a blue lead ore, very rich in filver, . perhaps
beyond any in England befides : this ore, when only.drefled, fells
fi» eight pounds a ton, which is about-the value of lead itfelf; one
o f the proprietors, and firme o f the workmen, averred, that,a ton
of this lead yields one hundred and forty ounces of filver : the vein
of ore was about a foot over, but in feme parts near three feet,
and about fifteen fathom deep.”
Lead is for the moft part o f a greyilh blue colour in the mine,
not much unlike what it is in the metallic Hate- O f this kind
there are feveral forts; asj firft, potter’s or teflellated ore, confift-
ing of a fhining, redangled, tabulated ftru&ure, and always breaking
into granules o f like parallelopiped fhape; and, when lead is
cheap, this ore, well cleanfed, is worth about fix pounds, a ton.
This is found in Sithney, Camborn, and many other parts of Cornwall.
Secondly, that which is o f a, flaky, fmooth, and glofly texture,
not breaking into cubical dies, but more ponderous, and therefore
containing more lead. Thirdly, a very clofe-grained ore, breaking
into an uneven fparkling furface like a grey tiflue, very rich in
filver. This is fcarce in Cornwall
c Boefh, by Shaw, page 59.
d In the parHhes of St. Meran, Boconck, Piran-
Sands, St. Agnes, Crowan, Sithney, Gwinear,
St. Ifly, St. CoTumb, lilogan, and Camborn. The
works moft noted formerly, are thole of Penrofe,
Penwortey, Trevafcus, Reliftian, and Guamek.
See Woodward’s Cat, vol. I, page 217, 218, and
voL IT. page 30*
• Woodward's Cat. vol, II. page 28, line 22.
r Some of it was fent me from the works at
Beerferris in Devonshire, and I have it alfo from
Cardiganshire in Wales. There is a mock -lead
very mining, and like the true of this colour}
the irregular fhape and texture of its granules,
and its want of weight, will difeover it. By fire,
it will divide into a powder, which may be ftrewed
upon writing.
Lead
Lead is foriWafaes'/found for'inról ved and hfddè im^a r, that,
were it not for its eminent weight, no metal would be fufpeded.
Some of tins fpaT is like a pumice-ftone8, fome granblated, others of
5a fibrous ftria£e|yfexture, like. the fplinters of> a bone glewed toge-
^ther, and of a brownifh colouf‘,|^gtofeof a tabulated cryftal, making
■ IMe &b no effe^dfcence with aqua forth, of a whitfth ochroustij
lour, . tvaïnfpare^fe another fovt'*ofwhit© tranfparent fpar in ftraigbt-
rlined xMumnaE Jlrhz, from Cardiganfhire in Wales,"of which WO have
fomekHb m England^dme this metal are cavetnous,-in green
'Cryftals, Whi^i^e^&'atoe'ï^; it is found in
tieautifai colodrSy in Mendip hills Somerfetihire, 'in Denbighfhiife,
-and at Pentós i^COPnwalK fj O f like forit, but in a möre ochröus
feeder, I have -feen le&d^ore broke in the tenefnönt 'of Nartfkêg, in
Slogan- parifl4,‘bedded in a y ellow 'd^ o f the ’Cxd^ fcofonr'f$£ ful-
phur, with out' any. other fulphüreoüs • fign but that 'óf cèlout^vé^ir;
"heavyand; > reckoned ■'rich in lead. '** This laft 'tire is vdriegkted in
fit. Ifly works,,;Cornwall-1. We have aifo*in Cornwall a" fölïabèous
talky kind of lead-mfe, but- what I havé foen is light iti róinpanfon,
and of lefe.beauty than The ftriated talky 4ead'-ore from Ireland,
which is. white;: fpeckled with purple, and exhibits very elegant
ipeeimetas. Leadd^feldom^fome think nëvèr ietmd in a native, that
fe : hi a metallic flate; but Dr. Woodward “ has given us an account
o f ^one fpecunen of this kind, and Linnaeus has native lead found
in Germany, which he calls Plumbum nudum (Syfr.1 Nan f84,
N°. I.) Lead is alfo laid to be found compleat and malleable in
a mine fif,The ifiahd Jamaica. It is however veiy fcarce, and in
general, i f lead-ore will yield three parts in four of the metal,1 (vhs.
feveaty-five out o f one hundred) it is reckoned very rich, but if
it yields- Only forty out of one hundred, itrtsi not worth working,
unlels eafy to come at. Lead-ore may be very rich in lead, and yet
Hot afford one grain of filver; and, on the other hand, the ore which
is poor in lead, does fometimes yield filver plentifully. As to the
potter’s ore, the finaller the grains the more filver they are likely to
contain, and vice verfdI ; but where-ever filver is found incorporated
with lead, extracting the filver does by no means impoverifh i t ;
if the aflay be ildlfully performed, it leaves the lead in a better and
more ufeful ftate than it was before 0; but lead is very apt to' con-
fume and lofe of its weight every time it is melted; upon this, and
many other accounts therefore, it requires a ikilful hand to make
the moft of it.
From Turkjr. -
From Tipperary, in Ireland.
From Ireland.
See Woodward’s Cat. vol. II, page 28.
1 Ibid. vol. I. page & it,
m Ibid. vol. II. page 28, 1. 23.
n Grew’s Muf. R. S. page 329.
0 Sir Hum. Mackworth, page 41.
Our