sedimentary

Chert Nodule

Microcrystalline Quartz (SiO2)

Hardness: 7 (Mohs), Color: tan to creamy orange, Luster: waxy to dull, Structure: cryptocrystalline, Cleavage: none (conchoidal fracture), Specific Gravity: 2.6

Identified July 14, 2026More sedimentary →

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Physical properties

Hardness: 7 (Mohs), Color: tan to creamy orange, Luster: waxy to dull, Structure: cryptocrystalline, Cleavage: none (conchoidal fracture), Specific Gravity: 2.6

Formation & geological history

Formed via the replacement of carbonate minerals by silica-rich fluids in limestone or chalk beds, often involving biochemical precipitation from organisms like sponges or diatoms. Deposits occur in sedimentary layers of various geological ages.

Uses & applications

Historically used for stone tools (flint) due to sharp edges; currently used for landscaping, road base, or as interesting gravel specimens for collectors.

Geological facts

This specific nodule shows a rounded, 'potato-like' morphology characteristic of chert nodules found in weathered limestone. Chert is so durable that it often remains behind after the surrounding host rock has eroded away.

Field identification & locations

Identify by its high hardness (it will scratch glass) and waxy texture. Commonly found in riverbeds, fields, or road cuts near limestone formations. Collectors look for unique shapes and internal banding.