sedimentary

Chert (Yellow Jasper)

Microcrystalline Quartz (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Ocher, tan, or yellow; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7. It has white quartz veins running through it.

Hardness: 6
Color: Ocher, tan, or yellow
Luster: Dull to waxy

Identified July 7, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed primarily from the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation in marine environments. This specimen has been water-worn and smoothed, likely in a river or beach environment.

Uses & applications

Historically used for making stone tools due to its sharp edges when broken. Today used in lapidary work, jewelry (as 'Jasper'), and as decorative landscaping stone.

Geological facts

Yellow jasper is often associated with iron inclusions (goethite or limonite) which provide its earthy color. Because of its hardness and toughness, it survives long-distance transport in rivers and along coastlines.

Field identification & locations

Identify by its smooth, waxy surface, extreme hardness (it will scratch glass), and characteristic conchoidal fracture pattern. Common in riverbeds and along glacial till deposits.

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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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Sandstone Grain

Clastic Sedimentary Rock Grain (SiO2 dominated)

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Chert Breccia

Brecciated Chert (Microcrystalline Silica)

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Shale or Slaty Mudstone

Argillaceous sedimentary rock

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Sandstone

Arenite (primarily SiO2)

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