61 
forms an ingredient of the glazing of common earthen¬ 
ware, which is usually readily acted on by weak acids, it 
is necessary to be very careful in this respect. 
generally chemically pure, but for the most part contains 
traces of antimony, copper, silver, and gold. All pre¬ 
parations of lead are poisonous, and as the oxide of lead 
PLATE XX. 
Fro. 1—3 .—Galena, Lead-Glance, Sulphueet of Lead. 
The primary form is the cube (Fig. 1), which is also 
of most frequent occurrence. Truncation of the edges 
and angles (Fig. 2) are also found, as well as regular 
octahedrons, and combinations of this with the rhombic 
dodecahedron (Fig. 3 D), cube (H) and pyramidal oc¬ 
tahedron (I) ; twins, dense, foliated, and crystalline 
granular, and perfectly compact masses also occur ; the 
last-named variety being called galena. The colour is 
lead-grey, sometimes with a black or variegated tarnish, 
the streak is lead-grey, and it makes a black mark upon 
paper. The faces of the crystals are not unfrequently 
striped in clusters, or run together, as it were, and the 
angles and edges are also sometimes rounded off. The 
metallic lustre is brilliant, especially in a fresh fracture, 
dazzling in the finely granular and compact varieties, 
the fracture is even, the hardness = 2A, and the specific 
gravity 7*4—7*6. The composition is simple sulphuret 
/ 
of lead, Pb, composed of 1 equivalent of lead (86*55) and 
1 equivalent of sulphur (13*45). There are also zinc, anti¬ 
mony, copper, and silver-lead ores, and part of the sulphur 
is sometimes also replaced by selenium. The silver-lead 
ores are only rarely crystallised, being generally finely 
granular and of lighter colour, the granular lead ores espe¬ 
cially are more or less rich in silver. The silver is con¬ 
tained in it as sulphuret of silver, and the amount of silver 
varies from i of an ounce to 3 ounces in the cwt. Com¬ 
pact lead ore usually contains sulphuret of antimony, that 
containing zinc-blende is recognised by its brownish colour, 
and that which contains copper by the disseminated yellow 
points or grains. There are also earthy lead ores, black 
lead ore, of blackish colour and dazzling appearance. 
Before the blow-pipe it melts easily and gives off sulphu¬ 
reous vapours; on the charcoal it becomes coated with 
the yellow oxide of lead, which may be easily reduced to 
small globules of lead, and the lead may be reduced and 
evaporated with evolution of white fumes, in iridescent 
colours, and on cooling the test is covered with yellow 
needles. Lead is readily beaten out with a hammer. A 
small amount of arsenic being present may be recognised 
by its peculiar odour, resembling that of garlic, and a 
similar quantity of selenium by the odour of horse-radish, 
while antimony gives a dense, white, inodorous smoke, and 
a coating on the charcoal, which is easily blown off. The 
silver in it can be most easily obtained by first reducing 
the heated lead ore and refining it with bone ashes, by 
which process the grain of silver is at last left behind. 
The tests in the moist way are still more certain, if 
the reduced grain of lead be dissolved in pure nitric acid, 
and the silver deposited by common salt. 100 parts of 
the washed, dried, and melted chloride of silver, contain 
75*33 of silver and 24*67 of chlorine. The test may be 
made shorter if the separation of the chloride of silver be 
obtained by a filtered solution of common salt, when the 
amount of silver may be reckoned by the proportion of 
the precipitate to the solution employed. 
Galena is the most widely distributed of lead and 
silver ores, and is therefore, wherever it occurs in con¬ 
siderable quantities, as, for instance, at the Harz, the 
Erzgebirge, in Nassau, the Black Forest, etc., smelted into 
lead. It is found usually in veins or beds, in the primary 
as well as in the older stratified formations. The finest 
crystals are found at Clausthal, and Neudorf in the Harz, 
Tarnowitz in Silesia, Przibram in Bohemia, Derbyshire, etc. 
When lead-glance is silverless, and occurs pure, it is 
brought into commerce as lead-ore, and applied to the glazing 
of earthenware. The lead obtained in the process of refining- 
forms a more or less pure oxide of lead, and is sometimes 
brought into commerce by itself, sometimes applied to the 
manufacture of red lead, and sometimes reduced to metallic 
lead and made into bars; the refined silver remaining 
behind is finely calcined, and is usually made into bars. 
The weissgiltigerz is a lead ore rich in silver, and con¬ 
taining sulphuret of antimony, sulphuret of zinc, and 
sulphuret of iron, and sometimes also copper, which con¬ 
tains 5—20 per cent of silver, and sometimes resembles 
grey copper ore. It formerly occurred plentifully at Frei¬ 
berg and Joachimsthal. 
The seleniuret of lead, of 2*5 specific gravity, similar 
in appearance to the foliated lead-glance, evolves before 
the blow-pipe strong- vapours of selenium, with the odour 
of horse radish or rotten cabbage, and gives a yellow bleb, 
and finally a grain of lead. It is found at Tilkerode and 
Zorge, also at the Lorenzo mine at Clausthal, etc., in the 
Harz, where seleniuret of cobalt also occurs. Seleniuret 
of lead and copper, and of quicksilver and lead, are like¬ 
wise found at Tilkerode. 
The compounds of the sulphuret of lead with sul¬ 
phuret of copper, and sulphuret of antimony, which have 
been called bournonite, needle-ore , and boidangerite, also 
those which consist of sulphuret of lead and sulphuret 
of antimony, such as zinkenite, jplagionite, geocronite , and 
jamesonite, we can only mention by name. 
Compounds of the Oxide of Lead. 
The compounds of lead with acids have more of a 
scientific than a practical interest, partly because they 
only occur in small amount, and partly because they are 
applied to no special use; on the other hand, a variety 
of them are very remarkable, partly on account of the 
beauty and brilliancy of the crystals, partly on account 
of the rarity of the acids found in combination with them 
(chromic, molybdenic, and vanadic acids), so that these 
lead ores form an ornament to collections. 
Fig. 4—8.—White Lead Oee, Caebonate of Lead, 
Ceeusite. 
Crystallises in rhombic octahedrons, with cleavage in 
