Chert (Green variety)

Physical Properties

Hardness: 7 (Mohs scale), Color: Sage to seafoam green, Luster: Waxy to dull, Crystal structure: Microcrystalline/Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific gravity: 2.6-2.7

Formation & Geological History

Formed through the accumulation of silica-rich organic remains (like diatoms or radiolaria) or from the chemical precipitation of silica in ocean water. These specimens often originate from Mesozoic or Paleozoic marine deposits.

Uses & Applications

Historical use for stone tools and arrowheads due to sharp edges; currently used for lapidary work, landscaping, and high-quality specimens are used for jewelry cabochons.

Geological Facts

Chert is so hard it can strike sparks against steel. The green color is typically caused by trace impurities of iron or chlorite within the silica matrix.

Field Identification & Locations

Identify by its 'glassy' or waxy feel and shell-like (conchoidal) fractures. Often found in riverbeds or coastal areas where sedimentary layers have eroded. It will scratch glass easily.

Identified on: 4/15/2026

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