color,
as this was the tint most prized in early times. Green jasper was also
called emerald in some instances. The banded varieties were much used
for cameos, specimens of which are still extant. By taking advantage of
the colors of the different layers, colored objects were made, such as
one which shows the head of a warrior in red, his helmet green, and
breastplate yellow.
Jasper
worn as an amulet was regarded a preventive of sorrow, and mottled
jasper suitably engraved was believed to protect its wearer from death
by drowning. It was a charm against scorpions and spiders, and
strengthened the chest, lungs and stomach, according to beliefs held in
the Middle Ages.
Basanite, also
known as Lydian stone, or touchstone, is chiefly used for trying the
purity of metals. Its value for this purpose depends on its hardness,
peculiar grain, and black color. Different alloys of gold give
different colors on the stone, and thus enable one to determine the
fineness of the gold. Also, if an object is plated, by giving it a few
strokes on the stone, the different color of the gold and base will be
revealed. Basanite is a black variety of crypto-crystalline quartz,
differing from jasper in being tougher and of finer grain, and from
hornstone in not being splintery.
Flint is
likewise an opaque quartz of dull color. It differs from jasper in
breaking with a deeply conchoidal fracture and a sharp cutting edge. It
is also often slightly transparent, and has a somewhat glassy luster.
These properties have led to its extensive use by the Indians and by
nearly all primitive peoples for the manufacture of weapons and
implements. Hornstone is more brittle than flint, and has a splintery
rather than a conchoidal fracture. A number of other subvarieties of
crypto-crystalline quartz occur, but they are not important as gems.
