sedimentary

Chert (Jasper/Common Opal mix)

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 on Mohs scale. Color: Tan, yellow, brown, and white banding. Luster: Waxy to vitreous. Crystal Structure: Trigonal (microcrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6-2.65.

Hardness: 6
Color: Tan, yellow, brown, and white banding
Luster: Waxy to vitreous

Identified June 30, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed primarily through the accumulation of silica-rich organic remains (like radiolarians) or the chemical precipitation of silica in seawater or groundwater. This piece appears to be a stream-tumbled nodule or fragment.

Uses & applications

Used historically for stone tools due to its sharp edges when fractured. Currently used in jewelry making (lapidary), as aquarium stone, and for specimen collecting.

Geological facts

Chert and Jasper are essentially the same material, but are named based on color and opacity. It is one of the most durable rocks on the planet and can survive millions of years of erosion.

Field identification & locations

Identified by its waxy luster, smooth conchoidal (shell-like) fracture edges, and extreme hardness (it will scratch glass). Commonly found in river beds or sedimentary outcrops.

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Sandstone or Siltstone

Arenite (if sandstone)

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Cone-in-cone structure (Limestone)

Cone-in-cone structure (Secondary Sedimentary Structure)

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Chert Breccia

Brecciated Chert (Microcrystalline Silica)

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Sandstone Grain

Clastic Sedimentary Rock Grain (SiO2 dominated)

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Shale or Slaty Mudstone

Argillaceous sedimentary rock

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Sandstone

Arenite (primarily SiO2)

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