from
Alaska shown in the accompanying colored plate. Sometimes the crystals
attain considerable size. Perfect ones from Colorado weighing fifteen
pounds are known, and some two feet in diameter are reported from North
Carolina. A curious feature of garnet crystals is that of often
inclosing other minerals. The garnets from New Mexico, for instance,
when broken open are sometimes found to contain a small grain of
quartz. In the crystals from East Woodstock, Maine, only the outside
shell is garnet, and the interior is calcite. Other crystals are made
up of layers of garnet and some other mineral.
Garnet
has a strong tendency to crystallize, and hence is usually found as
crystals. The grains of garnet found in the sands of river beds and on
beaches, though not often showing crystal form, may be really fragments
of crystals. Garnet is one of the most common constituents of such
sands because of its hardness and power of resisting decay. These
properties enable it to endure after the other ingredients of the rocks
of which it formed a part have been worn away. It is quite heavy as
compared with the quartz, of which the sand is mostly composed, and
hence continually accumulates on a beach, while the quartz is in part
blown away. In such localities it will always be found near the water
line, because the waves, on account of its weight, can carry it but a
slight distance inland. Practically all garnet is three and one-half
times as heavy as water, and some four times as heavy. As a rule, it is
somewhat harder than quartz, its hardness being 7-1/2 in the scale of
which quartz is 7. Some varieties are, however, somewhat softer. Most
varieties of garnet fuse quite readily before the blowpipe, and the
globules thus formed will be magnetic if the garnet contains much iron.
The green garnet, uvarovite, is almost infusible, however. Garnet is
not much affected by ordinary acids, although it may be somewhat
decomposed by long heating.
The name garnet is said by some authorities to come from the Latin word granatus, meaning
like a grain, and to have arisen in allusion to the resemblance of its
crystals in color and size to the seeds of the pomegranate. The German
word for garnet, granat, is the same as the Latin word. Others
think the word derived from the Latin name of the cochineal insect, in
allusion to a similarity in color.
The
use of garnet for gem purposes seems to date back to the earliest
times. Among the ornaments adorning the oldest Egyptian mummies there
are frequently found necklaces containing garnet. The Romans prized the
stone highly, and it is a gem much used at the present day, its
hardness and durability and richness and permanency of color giving it
qualities desirable for a precious stone.
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