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Quartz
Gems
Sardonyx
consists of bands of Sard, alternating with black and
white layers. Onyx is black and white banded chalcedony.
Black onyx ,ilk, sold today is generally artificially
blackened chalcedony. . colored "onyx" in
shades of red, blue, green, and yellow is Chalcedony
dissolved in circulating groundwater may replace buried
wood and vegetation
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The
replacement is so slow and delicate that even the cell
structure of the original wood is sometimes preserved.
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I wood, most notably from Arizona,
can be very colorful, and entire petrified trunk and limb
sections make interesting curiosities. Another name for massive
silicon oxide is silica, and wood replaced by chalcedony is
sometimes called silicified wood.
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Quartz Gems |
| Quartz
Gems
Most
of the chalcedonies are cut as cabochons or polished
slabs, sometimes in unusual or fanciful forms.
Chalcedony is ideal for carving and engraving,
fashioning into beads, spheres, and bowls, and
for making paperweights, pen holders, bookends,
and boxes. Huge quantities agate and jasper are
tumble-polished for use in inexpensive jewelry.
. 
The
city of Idar-Oberstein in West Germany has been
an important gem- cutting center since the year
31 AD- The entire city is dedicated to w of gem
cutting and carving, and houses some of the great
gem craftsmen of the world. |
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German
cutting has become synonymous with high quality. A variety
of materials is cut, but the chalcedonies occupy a n tremendous
importance in the area of large-volume low-cost gems.
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