sedimentary

Yellow Chert (Yellow Jasper)

Silicon dioxide (SiO2)

Hardness: 6.5-7. Mohs scale. Color: Yellow to tan with brown impurities. Luster: Dull to waxy. Crystal structure: Microcrystalline/Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.6-2.7.

Hardness: 6
Color: Yellow to tan with brown impurities
Luster: Dull to waxy

Identified July 6, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich fluids in sedimentary environments or the replacement of limestone by silica. The yellow color is primarily caused by goethite or limonite (iron oxide) inclusions.

Uses & applications

Used as a landscaping stone, in lapidary work for cabochons and tumbled stones, and historically used for stone tools due to its sharp conchoidal fracture.

Geological facts

Chert and Jasper are essentially the same mineral; Chert is generally the name for the sedimentary rock, while Jasper is the name used when the specimen is opaque and colorful enough for gemstone use.

Field identification & locations

Identify by its hardness (it will scratch glass), its smooth waxy feel when polished by water, and the way it breaks into curved, shell-like (conchoidal) surfaces. Commonly found in riverbeds and coastal regions.

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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Chert Breccia

Brecciated Chert (Microcrystalline Silica)

sedimentary

Sandstone Grain

Clastic Sedimentary Rock Grain (SiO2 dominated)

sedimentary

Shale or Slaty Mudstone

Argillaceous sedimentary rock

sedimentary

Sandstone

Arenite (primarily SiO2)

sedimentary