tribution
of gems is exceedingly irregular, and their market price varies within
wide margins, from circumstances of fashion, supply, general financial
conditions, etc.
Yet
these contingencies might doubtless be largely overcome by intelligent
and broad-minded management, such as has been conspicuously displayed
in the conduct of the diamond mines of South Africa. Not only is the
mining here conducted according to the most approved systems of modern
engineering, but equal attention is paid to placing the gems upon the
market, so that an over-supply shall not reduce the price. Some further
account of this will be found in the chapter on the Diamond.
Regarding
the influence of increase of depth upon the distribution and quality of
the gem minerals, no principles have been established as yet. It is
known that veins of amethysts, for instance, have turned entirely
colorless on penetrating below the surface, so that a valuable stone
became with depth worthless. On the other hand, improvement in color
and quality of stones below the surface, as compared with those above,
may often be reasonably expected, since the latter are more exposed to
disintegration and weathering, and the fading effects of light.
In
the mining of gems in a small way the amateur is likely to make the
mistake of resorting to the use of too much powder or other explosive.
While the rough work of exploration may wisely be carried on by means
of blasting, the actual removal of the mineral from the matrix should
usually be performed, where possible, by picks and chisels, in order to
avoid the shattering and breaking of pieces suitable for gems, which
often happens in blasting. Many fine gems have been lost through
carelessness in the work of mining, and while not all losses of this
kind can be avoided, with care and patience they can be reduced to a
minimum.
