Description

Agates mostly occur as nodules in volcanic rocks or sedimentary rocks, in which a cavity has been filled with silica(Quartz).  As groundwater passes through a cavity in the host rock, layers of silica are repeatedly deposited on the interior of the cavity, making the concentric bands agates are known for. Depending on what elements are present alongside the silica in the groundwater, varying colors of bands will be produced.  It is very unlikely that you would ever find an exact duplicate of any type of agate, Brazilian or other.