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mate, is dense and hard, and takes a high polish. Related
materials, usually gray or black in color, are chert
and flint. A pale, reddish chert with inclusions of
colorless quartz is commonly dyed blue and sold as "Swiss
lapis" or "German lapis," but these are
not the same as lapis lazuli pages 103-104).
Agate is chalcedony in which the coloration takes the
form of band or ¬wispy inclusions. Fortification
agate contains straight or concentric bands, while moss
agate displays colored or black mineral inclusions that
create fanciful landscapes and images in the chalcedony
matrix. Agates, like jaspers, occur throughout the world.
The tremendous variety of patterns has led to a wealth
of names, many of them for specific localities.
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The
finest moss agates come from India, and from Montana
Oregon, Idaho, and Wyoming. Agates from Arizona, South
Dakota, Mexico, and Brazil are known throughout the
world. The variety patterns and colors is almost endless.
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Much
commercial material is actually dyed chalcedony. Sard is basically
like carnelian, but tends to be more brownish and some what
Darker.
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Quartz Gems |
| Quartz
Gems
Chalcedony
is hard (7 on the Mohs scale), tough, and durable.
It’s fine grain allows for intricate and detailed
carving and design. The various colored and patterned
varieties have all been given individual and have
distinctive histories.
Carnelian, the modern spelling of the older "cornelian,"
was immensely popular in ancient Egypt and among
Mohammedans.color, ranging from light brownish-red
to deep clear red, is due presence of iron. Wax
does not easily adhere to polished car, which
made this material useful for seals. Natural carnelian
cornelian comes from Brazil, Uruguay, India, and
California.
Chrysoprase
is a highly translucent, apple-green chalcedony
frequently mistaken for jade. It is the most valuable
of the chalcedonies colored green by traces of
nickel silicate.
.
Chrysoprase,
usually cut into cabochons, beads, or cameos and
intaglios, was popular in the Victorian era. Much
of the "green onyx" and so-called Chrysoprase
today is dyed chalcedony. Fine natural Chrysoprase
comes from the Ural Mountains, California, Brazil,
and Australia.
Prase is translucent yellow-green chalcedony,
with little gem application.
Plasma is dark-green chalcedony with little translucency,
sometimes with white or yellow spots. Occasionally
iron minerals produce re, brownish spots, giving
rise to the name "bloodstone"
or "heliotrope.”
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Jasper
is a catch-all term applied to opaque, colored chalcedonies.
Often jasper displays no pattern, but the body coloration
is usually heavy and rich, in shades of brown, red, green,
and yellow. |
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