sedimentary
Chert (Pink Chert/Jasper)
Cryptocrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale), Color: Pinkish-tan to brown, Luster: Dull to waxy, Crystal Structure: Microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: Pinkish-tan to brown, Luster: Dull to waxy, Crystal Structure: Microcrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
Formation & geological history
Forms through the precipitation of silica from seawater or groundwater. Commonly found in nodular or bedded forms within limestone or volcanic ash deposits from various geological ages.
Uses & applications
Historically used for stone tools and weapons due to conchoidal fracture. Modernly used as an abrasive, for landscaping, or as semi-precious gems in lapidary work.
Geological facts
Chert is so hard it can strike sparks against steel. It was used extensively by prehistoric humans to create sharp edges for arrowheads and scrapers.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by a steel knife) and its smooth, shell-like (conchoidal) fracture surfaces. Commonly found in stream beds and outcrop exposures.
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