64 
Fig. 23—27.—Zinc Ores. 
Zinc, or spelter, as it is also sometimes named, is a 
bluish-white metal of 6’862—7*2 specific gravity, which 
retains its lustre for a long time in the atmosphere, exhibits 
a crystalline foliated structure, and is tolerably hard and 
tough at an ordinary temperature. It breaks into pieces 
under the hammer when cold, but at a temperature of 
from 212° to 302° Fahr. is very ductile, so that it can be 
extended into plates and wire, but at higher temperatures it 
again becomes friable, so that it can be reduced to powder. 
It crystallises in certain circumstances in rhombohedrons, 
melts at 773°. 6 Fahr., takes fire in the air at a somewhat 
higher temperature, and burns with a bluish-white dazzling 
flame ; when heated in closed vessels it is distilled. It 
occurs native only very rarely and by exception, frequently, 
however, mineralised with sulphur and oxygen. The 
ancient Greeks were in the habit of forming a bronze-like 
alloy out of zinc ore and copper, without otherwise knowing 
the metallic zinc, which was first made known in the six¬ 
teenth century by Paracelsus ; it had, however, been known 
for many centuries previous to this by the Chinese. Zinc is 
the most electro-positive of all the heavy metals, and is 
therefore chiefly used for galvanic batteries and galvanic 
precipitates, as it throws down even iron from its solutions. 
It is used by itself for all kinds of artistic moulds, statues, 
ornaments, and the like; when rolled out into plates as 
coverings for roofs, the manufacture of water-pipes, &c., 
in the fabrication of brass and bronze, for the preparation 
of sulphate of zinc and other chemicals. 
Fig. 23.—Blende, Sulphuret op Zinc. 
The primary form is a rhombic dodecahedron, Plate II., 
Fig. 8, which is, however, usually in combination with the 
octahedron, as in Plate XX., Fig. 23 ; octahedrons, tetra¬ 
hedrons, icosahedrons, and twins, crystalline-foliated, fibrous, 
compact, scaly, and stellate masses are also found. The 
crystals are of adamantine lustre, of remarkable foliated 
structure, and admit of cleavage in the direction of the 
dodecahedral faces. The colour is light-yellow passing 
into reddish-brown and black ; the streak is lighter; the 
hardness = 3*5—4, and the specific gravity 3*9—4*0. 
/ 
Pure blende is simple sulphuret of zinc, Zn, composed 
of 66*90 of zinc and 33*10 of sulphur; all the strongly- 
coloured varieties, however, contain, some of them sulphuret 
of iron, others sulphuret of manganese ; others also contain 
sulphuret of lead, and the compact blende not unfrequently 
has some sulphuret of copper in addition. Before the 
blow-pipe blende decrepitates, gives off fumes of sulphur 
and zinc, which on the charcoal leave a yellow tarnish, 
which becomes white when cold, and, when wetted with 
a solution of cobalt, appears dark-green at a glowing white 
heat. When melted with soda in the inner flame, metallic 
zinc is separated, which then burns. Should the blende 
contain cadmium, as for instance the stellate blende of 
Przibram, the zinc tarnish presents a brownish ring. 
Blende is a very widely distributed mineral, which 
occurs in all formations, from the primary rocks to the 
mussel-chalk. The finest crystals are found at Kapnik 
and Schemnitz in Hungary; at the Harz and Erzgebirge, 
where it occurs in large quantity, it is smelted for zinc. 
Fig. 24.—Oxide of Zinc and Franklinite. 
The red oxide of zinc crystallizes in right rhombic 
prisms, but is only found in crystalline foliated masses 
(Fig. 24), of a brownish-red colour, translucent, of ada¬ 
mantine lustre, brittle, of 4*0—4*5 hardness, and 5*43 
specific gravity, but sometimes also in the form of a white 
powdery efflorescence. The latter consists of pure oxide 
of zinc, Zn, the former contains 4 —12 per cent, of oxide 
of iron and manganese. It is easily reduced with soda, 
and is soluble in acids without effervescence. 
Franklinite crystallises in regular octahedrons, with a 
corresponding arrangement of laminae, which are, however, 
for the most part truncated at the edges, as in Fig. 24. 
It is also found compact or in roundish grains embedded 
in the red oxide of zinc, at Franklin and Sparta, in the 
United States. It is iron-black, passing into brown, has 
a dark-brown streak and slight metallic lustre, is opaque, 
of conchoidal fracture, 6*0—6*5 hardness, so that it gives 
feeble sparks on the steel, and a specific gravity of 5*09. 
The constituents are oxide of tin, protoxide of manganese, 
and oxide of iron, > Fe, in which the iron plays 
Mn) 
the electro-negative part. It melts before the blow-pipe 
to a black slag, and on the charcoal gives a zinc tarnish, 
leaving behind an iron slag containing manganese. 
Figs. 25 and 26.— Calamine, Carbonate of Zinc. 
The primary form is a rhombohedron of 107° 40', 
similar to that of calcite and spathose iron, with a corre¬ 
sponding direction of the laminae ; it occurs in crystalline 
aggregations, like those in Fig. 25, sometimes also with 
truncation and bevelling of the vertex, Fig. 26, or also in 
drusiform, fibrous, foliated, granular masses of a white, 
grey, or brown colour, generally coloured by hydrous oxide 
of iron. The streak is always somewhat lighter, the 
lustre slight, the fracture uneven to conchoidal, the hard¬ 
ness 5*0, the specific gravity 4*4—4*5, the crystals only 
are translucent. 
The pure white calamine is simple carbonate of zinc 
Zn C, consisting of 65*20 oxide of zinc, and 34*80 car¬ 
bonic acid, and is isomorphous with calcite, spathose iron, 
brown and bitter spars; the ordinary compact calamine al¬ 
ways contains a variable quantity of protocarbonate of man¬ 
ganese and iron, hydrous oxide of iron, alumina and silica, 
sometimes also a considerable quantity of carbonate of lime. 
It dissolves with effervescence in acids, and gives on 
the charcoal, especially with the addition of soda, metallic 
zinc, and the tarnish peculiar to it. Many calamines, the 
Silesian variety, for example, also contain cadmium, and 
give a reddish-brown ring on the charcoal. 
Calamine is the principal zinc-ore, and wherever it 
occurs in larger quantities, as, for example, at Altenberg, 
and Brillon in the Netherlands, Wiesloch in Baden, 
Tarnowitz in Silesia, at the Bleiberg in Carinthia, in Corn¬ 
wall, Cumberland, Derbyshire, Wales, and Lanarkshire, 
in Britain, and in North America, it is used for obtaining 
zinc, as well as for the manufacture of brass. 
Zinc-bloom is a carbonate of tin containing water, and 
occurs as a white incrustation in Carinthia. 
