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What do Agate Rocks look like?
By Mike Jozefiak
BEAUTIFUL AGATES
WHAT DO AGATE ROCKS LOOK LIKE.
Alas, in the natural state they are quite unprepossessing, resembling dull
looking potato-shaped rocks to the untrained eye. However, with some
experience you will be able to spot one with maybe a translucent,
coloured patch, showing the underlying agate through the eroded rock
surface. Go hunting on a sunny day helps accentuate this feature. Agate-
bearing rocks often have a pitted exterior, or maybe a waxy appearance
at a broken area of rock. Agates can often be found in stream beds or
on lake shores where the waters tumbling action over the millennia have
ground away the rough exterior and polished the agates into bright,
easily recognisable gems. Best to join a Rock-Hound club and learn how
to search for agates from the old timers!
HOW ARE AGATES FORMED.
It all starts with volcanic rock containing a lot of carbon dioxide & water
which bubbles out leaving a "Swiss cheese" texture. When water
containing dissolved silica with alkalis percolate through these holes, the
minerals are precipitated out slowly in the rock voids, producing those
glorious patterns & colours of Agates (agate is a form of Chalcedony,
which in turn is a form of Quartz, one of the most common minerals on
Earth). The alkali in the solution can attack any iron in the rock, producing
bands of iron hydroxide in spectacular forms and combinations with
other minerals present in the saturated solution. Agates have also been
found in Dinosaur bones, so high temperatures or pressures are not
required for their formation, just patience. These agates often maintain
the host original shape, after the host (tree, or root etc.) has eroded
away, hence their name of Limb Cast Agates
SOME COMMON AGATE TYPES:-
ONYX is a form of agate where the bands are white, alternating with
other bands of mainly black, but also of brown or red, depending on the
mineral composition of the surrounding area.
MOSS AGATE is a Dendritic Agate, looking like it has vegetative
inclusions (similar to Amber) but in reality, the Dendrites (from the Greek
Dendron - Tree) are usually minerals like oxides of Manganese or Iron,
which have percolated into cracks in the agate and then deposited out.
The transparency of the agate allows these dendrites to be seen within
the agate.
TURRITELLA AGATE are formed from the Turritell shells, a fossilised
marine gastropod with an elongated spiral shell or many whorls.
PETOSKEY AGATE is an agatized coral found in the Ottawa region of
Canada, chiefly around the town of Petoskey, in river beds.
AGATES are truly one of the most beautiful minerals, to be found in a
fantastic variety of colours, shades & patterns. When sliced and
polished, they are the "Crown Jewels" in any mineral collectors display!
About the Author
Visit http://www.trekking-hiking-outdoors.co.uk for more rocks & mineral information and where to buy your rockhound equipment!
Article Source: http://www.simplysearch4it.com/article/13181.html
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