Metals. 
MINERALOGY. Metals. 503 
acids, and giving a blue colour to hot fulphuric acid. 
Found at the Lead-hill in Scotland, in Carinthia, Britany, 
Burgundy, the Hartz, Auftria, &c. feldom maflive, difle- 
minated, or lamellar ; but moll commonly cryllallized in 
fmall cubic or rhombic or eight-fided plates, rarely in fix- 
fided prifms. Colour various lliades of yellow with a 
waxy lultre, and generally fomewhat tranfparent, with a 
white ftreak: frailure conchoidal. Before the blowpipe 
it decrepitates, and melts into a yellowilh and blackifh- 
grey mafs, producing globules of lead. Contains oxyd of 
lead 64^42, molybdic acid 34^2 5. 
9. Plumbum virens, green lead-ore, or phofphat of lead : 
greenifh, ponderous, breaking into indeterminate frag¬ 
ments, and reducible to a yellow powder ; nearly loluble 
in hot nitric acid without eftervefcence ; melting before 
the blowpipe, and cryflaliizing on cooling. Found in the 
lead-mines of Great Britain, New Spain, Siberia, Bohe¬ 
mia, Germany, Carinthia, &c. maflive, difleminated, or 
cryllallized in fix-lided columns variously modified. Co¬ 
lour various lhades of green, with often a mixture of yel¬ 
lowilh, greyilh, or reddilh brown, fliining, femi-tranfpa- 
rent, with a greenilh-white llreak and yellowilh powder: 
before the blowpipe it melts eafily, and cryllallizes on 
cooling: in muriatic acid it is foluble, and becomes 
decompofed: texture foliated, fraCture inclining to 
conchoidal: fpecific gravity from 6^27 to 6 - 56. A fpe- 
cimen from Wanlock-head contained oxyd of lead 80, 
phofphoric acid 18, muriatic acid r62. 
10. Plumbum jaipideum, or Itony lead : brown, hard, 
opake, of a common form. Found near Salka on the Car- 
pathic mountains, and contains 36 per cent, of lead, and 
a little filver and gold. 
11. Plumbum fulginofum, or footy lead-ore: black, 
without lullre, foiling the lingers, not totally foluble in 
nitric acid, emitting fulphurous flame and vapours be¬ 
fore the blowpipe, and cryflaliizing on cooling. Found 
at Freyburg, and in Brittany; and, befides oxyd of lead 
and phofphoric acid, contains fome fulphur: it may pro¬ 
bably be only a fulpliuret of lead in a decompofing flate. 
12. Plumbum alvernicum, or arfenico-phofphat of lead : 
greenifh-yellow, without lullre, bubbling and emitting 
arfenical fumes before the blowpipe, and cryflaliizing on 
cooling. Found at Auvergne in France, in mafles, or 
cryllallized in fmall fix-fided prifms. Specific gravity, 
6’846. Contains arfeniat of lead 65, phofphat of lead 27, 
phofphat of iron 5, water 3. Fourcroy. 
13. Plumbum arfenicatum, or arfeniat of lead: without 
luflre; melting before the blowpipe,, but not cryflaliizing 
on cooling; emitting arfenical fumes when heated to 
whitenels, and leaving a bead of lead. Found in the 
mines of Burgundy and Andalufia, in quartz or fellpar, 
and in fmall mafles. Colour pale-green or yellowifh- 
green, with a waxy luflre: when thrown on hot coals, it 
ibon becomes white. 
14. Plumbum duplex, or arfenico-fulphat of lead : with¬ 
out luflre, before the blowpipe emitting arfenical and ful¬ 
phuric flame and vapours. Found at Auvergne in France, 
and confifls of oxyd of lead combined with the arfenical 
and fulphuric acids. 
15. Plumbum vitriolatum, vitriolated lead, or fulphat of 
lead : whitifh, without luflre, quite fixed, eafily melting be¬ 
fore the blowpipe without decrepitation or effervefcence ; 
not effervefcing with acids. Found in the lead-mines of 
Strontian in Scotland, in Anglefea, and in Andalufia, fome- 
times varioufly modified, but generally in very minute cryl- 
tals, and moflly above the beds of galena, from the decorn- 
pofition of which it feems to originate. It is partly folu¬ 
ble in water, and is foon reduced before the blowpipe. 
Specific gravity, 6-3. Contains oxyd of lead 71, fulphuric 
acid 24'8, water 2, oxyd of iron 1. Klaproth. 
Sulphat of lead is diflinguiflied from carbonat of lead 
by its infolubility in nitric acid : from molybdat of lead 
in being more eafily reduced by the blowpipe. 
16. Plumbumcorneum, or corneous lead: white,with¬ 
out metallic luflre, eafily melting before the blowpipe, 
and in a greater heat entirely evaporating. Found in the 
mines of Lotharingia and Bohemia. 
17. Plumbum plumbago, or compaft galena : with me¬ 
tallic lullre, eafily melting with fulphurous vapour and 
flame, and leaving a bead of lead without any mixture of 
filver. Found in the lead-mines of England and Scot¬ 
land, Norway, Sweden, Spain, Saxony, &c. in mafs, no¬ 
dular or fpecular. Colour lead-grey, and has a brighter 
ftreak texture compact, and generally breaks into in¬ 
determinate fragments. Specific gravity, 7-444. It con¬ 
tains merely lead combined with fulphur. 
18. Plumbum galena, common galena, or fulphuret of 
lead : of the colour and luflre of lead, ponderous, foft, 
prefenting granular concretions, breaking into cubical 
fragments, melting with fulphurous flame and vapours, 
and when the lead is reduced to a glafly oxyd leaving a 
bead of filver. 
Sulphuret of lead is met with in very great abundance 
in all parts of Europe ; and in noplace perhaps more abun¬ 
dantly than in England, notwithflanding the great length 
of time during which the mines have been worked ; and 
they appear to have been worked antecedently to the ar¬ 
rival of the Romans. Pliny, in fpeaking of the ores of 
lead, fays, “Nigrum plumbum in Hifpania totafque per 
Gallias laboriofe eruitur : fed in Britannia fummo terra 
corio adeo large, ut lex ultro dicatur, ne plus certo modo 
fiat.” The epithet nigrum is uled in order to diftinguiih 
the metal in queftion from tin, which at that time was 
very commonly called plumbum album. 
A great proportion of the lead of commerce is obtained 
from this ore; which is firfl roafled, in order to diflipate 
the fulphur, and then mixed with the neceffary quantity 
of coke or charcoal, and reduced in a common furnace. 
The lead, which remains after the operation of roafling, 
is in an oxydated flate : the coke or charcoal, with which 
it is mixed in the furnace, decompofes the metallic oxyd; 
and, combining with its oxygen, flies off in the form of 
carbonic acid gas, while the lead is reduced to a metallic 
flate, and finks to the bottom of the furnace. The melt¬ 
ed lead, after it has been withdrawn from the furnace and 
received into the bafon placed beneath, prefents a lingu¬ 
lar appearance in confequence of expofure to the air: 
for its furface is inflantly covered with a thin iridefeent 
pellicle, owing no doubt to the incipient flate of oxyda- 
tion produced by the union of the oxygen of the atmof- 
phere with the metal. The appearance is not unlike that 
fuperficial iridefcence which is often obfervable on natu¬ 
ral fpecimens of fulphuret of lead ; and which, perhaps, 
depends on a fimilar caufe; the fulphur having been pre- 
vioufly diffipated at the furface of the ore. 
Cryltals of fulphuret of lead are generally very diftinCl ; 
and are often found completely inl'ulated. M. Haiiy fays, 
that this is particularly the cafe with thofe cryftals which 
have the mixed form of the cube and oftohedron; and he 
adds, that in fome countries cryftals of this kind, previ- 
oufly rounded by attrition, are ufed as bullets. The ac¬ 
cidental fraCture of mod varieties of fulphat of lead fhows 
very diltin&ly a cryftalline cubic ftrufture; and the fub- 
flance readily feparates into fragments which approach 
more or lefs to a cubic form. In fome inftances there is 
a broad ftriated appearance, which is owing to the pre¬ 
fence of antimony ; that metal being difpoled to crystal¬ 
lize in acicular prifms. Other varieties are of a completely 
granular texture: to thefe the epithet jieel-grained is 
applied ; and it is often very difficult to diftinguiih them 
by the eye from granular grey iron-ore. 
Almoft every variety of fulphuret of lead contains a 
greater or lefs proportion of filver; and the granular va¬ 
rieties are fuppofed to contain the moll. The filver, af¬ 
ter thereduftion of the lead, may be feparated by the pro- 
cefs of cuppellation : but in the greater number of in¬ 
ftances the proportion of filver is not fufficient to repay 
the trouble and expenfe of extracting it: and hence the 
lead of commerce almoft always contains fome portion of 
filver. A piece of common fheet-lead, of a circular form 
