Tin, in its pure state, has nearly the color and luster of silver. In
hardness, it is midway between gold and lead. It was known to the
ancients, who procured it from Spain and Britain, and appears to have
been in use in the time of Moses. It is rather a scarce metal, being
found in but few parts of the world in any considerable quantity.
Cornwall is its most productive source; it also occurs in the mountains
between Gallicia and Portugal, and in those between Saxony and Bohemia.
It has, also, been brought from Malacca, in India, and from Chili and
Mexico. There are but two ores of tin; one of which, the native peroxyd,
is the chief source of all the supplies of this metal, as the other ore,
which is the double sulphuret of tin and copper, sometimes called
_bell-metal ore_, is extremely rare.
Cornwall has been in all ages, famous for its numerous mines of tin,
which are in general very large, and rich in ore. The tin-works are of
different kinds, dependent on the various forms in which the metal
appears. In many places its ore so nearly resembles common stones, that
it can only be distinguished from them by its superior weight. In other
parts, the ore is a compound of tin and earth, concreted into a
substance almost as hard as stone, of a bluish or grayish color, and to
which the mundic, impregnated with copper, frequently gives a yellowish
cast. This ore is always found in a continued stratum, which the miners
call lode; and this, for the greater part, is found running through the
solid substance of the hardest rocks, beginning in small veins near the
surface, perhaps not above half an inch or an inch wide, and increasing,
as they proceed, into large dimensions, branching out into several
ramifications, and bending downward in a direction which is, generally,
nearly east and west. These lodes, or veins, are sometimes white, very
wide, and so thick, that large lumps of the ore are frequently drawn up
of more than twenty pounds’ weight. The lodes of tin ore are not always
contiguous, but sometimes break off so entirely, that they seem to
terminate; but the sagacious miner knows by experience, that, by digging
at a small distance on one side, he will meet with a separated part of
the lode, apparently tallying with the other end, as nicely as if it had
been broken off by some sudden shock of the rock.
The miners of Cornwall follow the lode, or vein, in all its rich and
meandering curves through the bowels of the flinty earth. The waters are
sometimes drained from the mines, by subterraneous passages, formed from
the body of the mountain to the level country. These passages are called
_adits_, and are occasionally the labor of many years; but when
effected, they save the constant expense of large water-works and
fire-engines. From the surface of the earth the workmen sink a passage
to the mine, which they call a shaft, and place over it a large winch,
or, in works of greater magnitude, a wheel and axle, by which means they
draw up large quantities of ore at a time, in vessels called _kibbuls_.
This ore is thrown into heaps, which great numbers of poor people are
employed in breaking to pieces, and fitting the ore for the
stamping-mills.
A third form in which tin appears is that of crystals; for this metal
will, under proper circumstances, readily crystallize. Hence, in many
parts of the mineral rocks, are found the most perfectly transparent and
beautiful crystals of pure tin. Beside these crystals, in many of the
cavernous parts of the rocks, are found those transparent crystals,
called Cornish diamonds, they being extremely brilliant when well
polished. The form is that of a six-sided prism pointed on the top, and
they are sometimes four or five inches in length. The value of the tin
exported from Great Britain, in 1853, the greater part of which came
from the Cornwall mines, was nearly six million dollars.