M1NERALOG 
Metals. 
504 
Metals. 
and about the diameter of a fixpence, the weight of which 
is about a hundred grains, will ufually afford by the pro- 
cels of cuppellation a globule of filver barely vifible to the 
naked eye. Where the proportion of lilver is fufficient 
to repay the expenfe of extraction, the procefs of cuppel¬ 
lation is fo contrived that the oxydated lead does not fink 
into the cuppel, but is feparated in the form of a ferni- 
vitrified nials called litharge. 
The minerals that ufually accompany fulphuret of lead 
are, fulphat of barytes, carbonat and fluat of lime, and 
quartz, among earthy fubftances; copper pyrites, fparry 
iron-ore, and fulphuret of zink, among metallic fub- 
ltances: the laft-mentioned fubflance fcarcely ever fails 
to accompany it. This ore ufually occurs in veins, and 
detached maffes, imbedded in folid data; fometimes, 
though rarely, in rounded nodules imbedded in marl or 
clay. Brogniart mentions an inltance of this kind in Si- 
lefia : and a fimilar inltance occurs in that mine, near Caf- 
tleton, where the blue fluor fpar of Derbylhire is quarried. 
There is a peculiar form of fulphuret of lead called 
JlivhevJides ■, a term expreflive of the fmoothnefs of its fur- 
face. It is a thin incruftation, which appears to have 
been depofited on the oppofite furfaces of natural cre¬ 
vices; thus forming a narrow vein. The fides of thefe 
crevices are barely removed from each other, yet are not 
actually in contact. In lome inftances th.is vein pene¬ 
trates to a confiderable extent: and its prefence is made 
known to the miner by a crackling noife, which is pro¬ 
duced by the blow of a hammer, or fometimes even the 
flighted fcratch of a pick-axe, againd the rock in which 
he is working: and the noife is ufually followed by an 
explofion of the rock, in the direction and neighbourhood 
of the vein. The caufe of this lingular effect is not at all 
underdood. 
Sulphuret of lead very clofely refembles fome varieties 
of fulphuret of zink; but the metallic ludre of the latter 
is dedroyed by fcratching the furface of the ore with a 
knife, which is not the cafe with the fulphuret of lead : 
if both are breathed upon, the ore of lead recovers its 
brilliancy in a moment; the ore of zink very gradually. 
Sulphuret of lead is didinguilhed from plumbago by its 
greater fpecific gravity; and by the comparatively faint 
trace which it leaves on paper.: the fame marks will ferve 
to didinguilh it from molybdenum ; which is, belides, of 
aloft foliated texture like talc, and has a confiderable de¬ 
gree of flexibility. 
19. Plumbum ferriferum, ferriferous lead-ore-, with 
metallic ludre, melting with fulphurous vapours and 
flame, but more difficultly than galena ; and, if the heat 
be increafed, forming a black glafs. Found in the mines 
of Sweden ; fometimes maffive, fometimes crydallized. 
Befides lead and fulphur, it contains fome filver and iron. 
20. Plumbum dibiatum, or antimonial lead-ore : of 
the colour and ludre of lead, fibrous, breaking into cruf- 
tofe fragments. Found in the mines of Siberia, Sweden, 
Hungary, and Spain ; of a compaCt and ftriated texture, 
with the pieces into which it breaks either draight or in¬ 
curved, and the fibres parallel orfafcicled ; when heated, 
it emits fulphurous flame and vapours. Befides lead and 
fulphur, it contains antimony and filver. 
21. Plumbum Hercynicum, or Hercynian lead-ore: 
combined with copper and antimony, a fmaller propor¬ 
tion of iron and fulphur, and a very fmall quantity of 
filver ; with metallic ludre. Found in the mines of An- 
dreafburg on the Hartz. Contains lead 34, copper 16-3, 
antimony 16, iron 13-7, fulphur 10, filver 2-3. 
22. Plumbum Cornubicum, or Cornifli lead-ore : com¬ 
bined with antimony, a fmaller proportion of copper and 
fulphur, and a very fmall quantity of iron ; with metallic 
ludre. Found in the mines of Cornwall; and contains 
oxyd of lead about 50, antimony 21, copper 14, fulphur 7, 
iron 2. Klaproth. 
23. Plumbum Subaudicum, or Subaudian lead-ore: 
with metallic ludre, emitting arfenical vapours before the 
blowpipe. Found in the mines of Subaudia; and confids 
of oxyd of lead, antimony, and arfenic. 
Plate VI. In collections of minerals, fays Knorr, (De- 
lices de la Nature.) it will be found in general, that ores 
of lead are the heavieft ; the reafon is, that, though pla- 
tina, gold, and quickfilver, are in themfelves heavier than 
lead, they are not found in fuch large maffes as to impart 
a confiderable fpecific gravity to the ore. He then gives 
us, rig. 1, grains of lead faid to be native ;- yet, as he ob- 
ferves, it is difficult to fuppofe that nature produced them 
in this form ; it would feem more reafonable to take them 
for drops of lead melted either by the hand of man, or 
elfe by a fubterraneous fire caufing the lead to run out of 
its matrix. 
Fig. 2 (from Raflileigh’s Cabinet) reprefents opake 
white ftriated lead-ore, diverging from different centres. 
From the filver-mines in Tipperary in Ireland. Fig. 3, 
white cryffals of lead-ore, forming rectangular plates, 
with the edges bevilled from ail fides, in the hollow part 
of an iron ore. Fig. 4, one of the cryffals of lead-ore a 
little magnified. From Huel Role, a mine near the Low 
Pool, Cornwall. Fig. 5, beautiful four-fided pyramidical 
cryffals of lead-ore joined bale to bafe, with the points of 
the angles truncated fo as to form parallelograms, having 
fmall fimilar cryffals, and blende, in fome parts of the tri¬ 
angular fides of the pyramids. Small cryffals of purple 
fluor and fmall cryffals of blende are fprinkled over the 
ftone, which is of a pigeon-neck colour. From Derbylhire. 
Fig. 6 is a cryftallized ore of lead : it is ponderous,/lark 
yet tranfparent; cylindrical, hexagonal, and pointed. At 
the bafe are fome portions of a polyhedral form, which 
have the natural colour of lead, with Alining facets. Fig. 7 
is a white fpathic ore of lead, PI. fpatofum, from the mines 
in the Hartz mountains in Germany. Here the meral 
imparts no tint to the ore, which looks like common 
fpar ; but its fpecific gravity, being fo much greater than 
common fpar, (hows the quantity of metal it contains. 
Fig. 8 is common lead-ore of a cubic form, with internal 
fquare figures, having the fides oppoled to the angles of 
the outward cubes. From Derbylhire. 
Fig. 9 is a fine fpecimen of galena with great cubes and 
broad ffriae. This ore is very rich, containing 60 or yolbs. 
of lead to the cwt. with 40 or 30 of fulphur. This ore is 
very plentiful in the mines of Saxony and Bohemia; it is 
always mixed with filver, though this fpecimen contains 
lefs than lome others. The cubes are compofed of thin 
foliations, laid one over another like leaves of paper; but 
the facets are more or lefs ftriated, not all even. The 
ftone is a quartz, with cubical fpar, of which lome layers 
are feen at the bafe of the figure. Fig. 10 is an ore of lead 
confining of a mixture of galena, foliated fpar, and mar- 
cafite : the fpar lies at bottom, and the yellow dots in the 
blackiffi ore are the grains of marcalite which have filled 
up the interftices. Thefe ores are pretty common in Italy, 
and particularly in the kingdom of Naples. Fig. 11 is 
galena with fmall cubes and narrow ftrias, in quartzous 
fpar. This differs from fig. 9, in having the lozenges and 
their foliations fmaller, more folid, and richer. 
Fig. 12 and 13, are ferruginous ores of lead, contain¬ 
ing about 5olbs. of lead in 100. They are more frequent 
in Lorraine than ellevvhere. The matrix is not a ftone, 
but an earth ; and the particles are partly loofe, appear¬ 
ing like finning dots, and partly fo mineralized with the 
earth, that the metal can only be prefumed by the weight 
of the ore, not being at all vifible to the eye. Fig. 14 is 
a green ore of lead, in a brownilh grey fpar. The green 
colour can arife only from particles of copper, which this 
ore is accordingly found to contain. Fig. 15 is an ore of 
crifped lead of a yellowilh-green colour. This is very 
rich, and contains copper like the preceding. The ma¬ 
trix is a quartz. 
Niccolum, Nickel.— Generic characters : Reddifh- 
white, hard, malleable, attracted by the magnet, and it- 
felf convertible into the magnet; fpecific gravity 9 ; fufing 
with 
