sedimentary
Likely brown chert (flint)
Microcrystalline quartz (SiO₂), variety chert/flint
AI-generated identification · may be incorrectHardness about 7 Mohs; opaque tan to brown with a waxy or dull luster and no visible crystals or cleavage. The sharp, curved fracture surfaces are characteristic of conchoidal fracture; identification from the image alone is uncertain.
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Physical properties
Hardness about 7 Mohs; opaque tan to brown with a waxy or dull luster and no visible crystals or cleavage. The sharp, curved fracture surfaces are characteristic of conchoidal fracture; identification from the image alone is uncertain.
Formation & geological history
Forms as silica-rich sediment or replacement material in sedimentary rocks, commonly limestone and chalk. Chert occurs in rocks of many ages and settings.
Uses & applications
Historically used for cutting tools and fire-starting; today collected or used for demonstrations and, locally, decorative stone.
Geological facts
Chert breaks into exceptionally sharp edges, making it an important prehistoric tool material.
Field identification & locations
Look for hardness sufficient to scratch glass, a smooth waxy surface, and curved fracture scars; common sources include limestone and chalk deposits worldwide. The specimen appears to be a chipped piece, but confirm with a hardness test and geological context.
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