is
a familiar fact that Organic Nature does not present an equal
development of life in every part of the world. Each country—or at
least each zone of climate—has its own fauna and flora—its peculiar
assemblage of animals and plants. No one needs to be reminded that the
animals and plants of the tropics are widely different from those of
temperate zones, while these again differ from those of the Polar
regions. But when we turn to the Inorganic world, we fail to
detect any similar laws of distribution. Climate, so far as we know, is
without sensible effect on the development of minerals and rocks. Many
minerals are common to the hottest and the coldest' parts of the world;
yet they present no discernible difference whether brought from
tropical or from Polar regions. It is true that occasionally there are
slight local differences in crystallization, or in other physical
characters, sufficient to enable an experienced mineralogist to say at
once from what district a given mineral has been obtained. But these
trivial differences are due rather to geological than to geographical
conditions, and climatic influences have nothing whatever to do with
the distribution of minerals.
Nor
is this general rule in any way broken by those exceptional minerals
which we distinguish as Precious Stones. It was a pardonable
supposition of ancient