AGATE
(CHALCEDONY).
Agate
occurs in nodular masses in rocks such as volcanic lavas.
When split open, they reveal an amazing variety of colours
and patterns, and a distinct banding that distinguishes
agate from other kinds of chalcedony (the compact,
microcrystalline variety of quartz). Band clours are
determined by the differing in purities present, although,
being porous, agate is often dyed or stained to enhance the
natural colour. Agate also occurs in several distinct forms.
Fortification agate has angularly arranged bands resembling
an aerial view of a fortress. Moss agate (or mocha stone) is
translucent and colourless, white or gray, with dark,
moss-or tree-like (dendrite) inclusions. It is Usually cut
as thin slabs, or polished as ornaments, brooched, or
pendants, Agatized wood is fossilizwd wood that has had its
organic matter replaced by gate.
Occurrence
Probably
the most famous area for agates is Idar-Oberstein in
Germany, where agate has been collected since 1548. It now
imports agates from the huge deposits in Uruguay and Brazil.
Moss agate occurs in the Hindustan are of India; also china
and the USA. The most famous agatized wood is found in the
Petrified Forest in Arizona (USA). Agate are also found in
Mexico, Madagascar, Italy, Egypt, India, China, and
Scotland.
CARVED
BOWL
Agate is a very
popular stone for carving and polishing, although bowl could
only be worked by an expert lapidary. The parallel banding
is typical of agate. |
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POLISHED
SLICE
Parallel
bands and patterns.
Agate
is often collected and polished by enthusiasts |
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STAINED
AND POLISHED
OVAL
more stain
taken up in some areas.
distinctive
concentric banding |
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MOSS
AGATE
ROUGH
Green, moss-like inclusions.
Whit quartz
crystals
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FORTIFICATION
AGATE
ROUGH
Parallel
but angular banding
Colourless
quartz crystals. |
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