sedimentary
Chert (Green variety)
Chert (Silicon Dioxide, SiO2)
AI-generated identification · may be incorrectHardness: 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
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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.
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