The geochemistry of agate and chalcedony in volcanic rocks represents an intricate record of silica precipitation and crystallisation processes occurring under variable thermal and chemical conditions ...

Forbes contributors publish independent expert analyses and insights. David Bressan is a geologist who covers curiosities about Earth. Chalcedony, from the Greek trade city of Kalzedon, is a variety ...

The mineral chalcedony is a microcrystalline type of quartz which replaces the original calcium carbonate of the coral and forms into agate. Grains of sand and pieces of the original calcium carbonate ...

Mineral deposits can create markings that look like forests or mountains, and experts say each stone is distinctive. By Jill Newman When Tarun Adlakha displays a dendritic agate, with its finely ...

L-23 (Little Colorado River Gravel Chert, Petrified Wood, Agate, Chalcedony): Not a direct collection from outcrop; Provenience includes samples from gravel deposits; Collection includes raw material, ...