sedimentary

Weathered flint or chert fragment

Microcrystalline quartz (SiO₂), likely chert/flint

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; pale gray-beige, dull to waxy luster, very fine-grained and non-cleaving. The rounded, weathered surface and possible conchoidal fracture are consistent with chert, though the photo alone cannot distinguish it confidently from weathered limestone or quartzite.

Identified August 9, 2026More sedimentary →

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Physical properties

Formation & geological history

Chert forms when microcrystalline quartz replaces silica-rich sediment or accumulates from biological silica; it occurs in sedimentary beds of many ages, commonly Paleozoic–Mesozoic. The specimen appears naturally weathered and water-worn.

Uses & applications

Historically used for sharp tools and fire-starting because it fractures conchoidally; today it is mainly a teaching or casual collecting specimen, with little industrial value in this form.

Geological facts

Fresh broken chert typically has sharp curved fracture surfaces and may be translucent at thin edges. Flint is generally the darker, often organic-rich variety of chert.

Field identification & locations

Test carefully for glass-like conchoidal fracture and inability to scratch it with a steel knife; limestone fizzes in dilute acid, while chert does not. Common in sedimentary regions and gravel deposits worldwide.