Brazilian Agate "Crystal"

Agate is a form of Chalcedony, made up of 90% quartz and 10% morganite. It is composed of microscopically fine fibrous crystals, and it normally shows color banding, stripes, whirls, bull's eye and other random patterns due to impurities in the quartz. Igneous rock is formed by lava and volcanic activity. This activity can form pockets / bubbles in the rock, similarly to Swiss cheese. When these pockets are formed in an area close to water, the water which is filled with minerals, (primarily quartz), is forced into the pockets, forming a layer of gel which eventually eats away the igneous rock. Layer upon layer of this gel is created until the void is filled and the water dries out, allowing for complete crystallization. These pockets can be broken up over time, then washed into the waterways, where it can be naturally smoothed and polished. Sometimes it will remain intact, and a void will not fill completely, as in the case of an Agate Geode. Agates were first discovered along the river Achates, in Sicily, for which they are named.