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