arranged, from an artistic point of view, into three very distinct sections.
The first includes all the stones formed of pure silica crystallized.
The second comprehends all the stones formed of pure silica not crystallized.
The
third includes the stones formed of silica, always nearly pure, but
containing some traces of colouring substances, which, however
insignificant their quantity, communicate, in a commercial and artistic
sense, a value to the stones that is altogether special.
In
the first group are placed quartz or rock crystal, and all its
varieties. The latter bear very different names in commerce, but their
composition is almost identically the same. If a piece of white silk
were cut into shreds, and each of these pieces plunged into a dye of
different tint and intensity, a different name might easily be given to
each fragment according to its colour; but its substance would still be
the same. Quartz holds the same relation to the precious stones of the
section we are about to consider, as the white silk would bear to the
tinted morsels we have described.
FIRST SECTION. QUARTZ.
Quartz, which is called also rock crystal, is one of
