sedimentary

Weathered chert or flint fragment

Microcrystalline quartz (SiO₂), likely chalcedonic chert with iron-oxide staining

AI-generated identification · may be incorrect

Hardness about 6.5–7 Mohs; cream to gray-brown coloration with rusty orange weathering, dull to waxy luster, and no visible cleavage. Its fine-grained microcrystalline quartz structure commonly produces a conchoidal fracture and sharp edges.

Identified August 27, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when silica-rich groundwater replaced or cemented sediment, often in limestone or chalk, during diagenesis; the exact geological age cannot be determined from the image. Brown coloration likely reflects iron-oxide alteration or surface weathering.

Uses & applications

Chert is used historically for cutting tools and fire-starting, and occasionally as aggregate or decorative stone; this irregular fragment has little commercial value.

Geological facts

Chert and flint are varieties of microcrystalline quartz; flint traditionally refers to dark chert, while lighter material is generally called chert.

Field identification & locations

Look for very fine texture, waxy appearance, high hardness, and conchoidal fracture; it should scratch ordinary glass and resist a steel knife. Common in sedimentary formations worldwide, especially limestone-bearing regions.