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Author: Mike Jozefiak
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
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 ( Next Page )
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