sedimentary

Jasper (specifically Chert or Orbicular Jasper)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Gray, tan, and creamy yellow; Luster: Dull to vitreous; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.58-2.91

Hardness: 6
Color: Gray, tan, and creamy yellow
Luster: Dull to vitreous

Identified June 29, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of silica-rich microfossils or chemical precipitation from hydrothermal fluids, often in marine sedimentary environments where silica replaces other materials over millions of years.

Uses & applications

Commonly used for lapidary work, jewelry (cabochons), talismans, and as decorative pebbles in landscaping or aquariums.

Geological facts

Jasper is an opaque variety of chalcedony. The swirling patterns in this specimen are often called 'orbicular' or 'banded' and are caused by impurities such as iron oxides or clays during the silica deposition process.

Field identification & locations

Identify by its extreme hardness (cannot be scratched by a steel knife) and its smooth, waxy feel when water-worn. Common in riverbeds and beaches worldwide, particularly in coastal volcanic regions.

Other sedimentary specimens

See all

Sandstone or Siltstone

Arenite (if sandstone)

Sedimentary

Cone-in-cone structure (Limestone)

Cone-in-cone structure (Secondary Sedimentary Structure)

sedimentary

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