sedimentary

Chert (often called Jasper or Flint)

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 (Mohs scale), Color: Red, brown, and gray variegation (impure), Luster: Waxy to vitreous, Crystal structure: Trigonal/Microcrystalline, Cleavage: None (conchoidal fracture), Specific gravity: 2.65

Hardness: 6

Identified June 21, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine or freshwater environments. This specimen likely formed as a nodule in limestone or chalk during various geological eras (Paleozoic to Cenozoic).

Uses & applications

Historically used for stone tools (knapping). Currently used for lapidary work, jewelry (beads/cabochons), and as decorative landscaping stone.

Geological facts

Because it breaks with a conchoidal (shell-like) fracture, it produces very sharp edges. Early humans used this property to create spearheads and knives. It is also often used as the 'flint' in flint-and-steel fire starters.

Field identification & locations

Identify in the field by its waxy texture, smooth conchoidal fractures, and ability to scratch glass. Commonly found in riverbeds, glacial deposits, and as nodules in sedimentary rock layers across North America and Europe.

Other sedimentary specimens

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Sandstone or Siltstone

Arenite (if sandstone)

Sedimentary

Cone-in-cone structure (Limestone)

Cone-in-cone structure (Secondary Sedimentary Structure)

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Sandstone Grain

Clastic Sedimentary Rock Grain (SiO2 dominated)

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Chert Breccia

Brecciated Chert (Microcrystalline Silica)

sedimentary

Shale or Slaty Mudstone

Argillaceous sedimentary rock

sedimentary

Sandstone

Arenite (primarily SiO2)

sedimentary