National Geographic News

Chert Granules

Photograph by Society of Economic Paleontologists and Mineralogists

A single pore between chert granules in a rock formation in Ontario Province, Canada, shows off its colors in this photomicrograph. This rock contained chalcedonic cement before it underwent diagenesis, a process where low temperatures and low pressures alter the content of sediments before they finally lithify, or turn into rock.

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