sedimentary
Chert (likely a flint-like piece)
Microcrystalline quartz (SiO₂), variety of chert
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; pale gray-white with rusty iron-oxide staining and a dull to waxy luster. It has no visible crystals or cleavage and breaks with smooth, curved conchoidal fractures and sharp edges.
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Physical properties
Hardness about 6.5–7 Mohs; pale gray-white with rusty iron-oxide staining and a dull to waxy luster. It has no visible crystals or cleavage and breaks with smooth, curved conchoidal fractures and sharp edges.
Formation & geological history
Forms when silica precipitates or replaces sediment in sedimentary settings, often as nodules in limestone or chalk. Its age cannot be determined from the image; chert forms across many geological periods.
Uses & applications
Used historically for cutting tools and fire-starting; attractive pieces are collected, and some varieties are shaped into decorative objects.
Geological facts
Chert’s conchoidal fracture can produce exceptionally sharp edges. The specimen’s shell-like fracture surfaces and dense, fine-grained appearance are consistent with chert.
Field identification & locations
Look for a very fine texture, hardness sufficient to scratch glass, and curved fracture scars; common worldwide in sedimentary formations. The image suggests chert, but does not establish its exact variety or locality.
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