sedimentary

Chert (specifically Yellow Jasper variety)

Silicon Dioxide (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Opaque yellow, tan, and earthy tones with iron inclusions; Luster: Waxy to dull; Crystal structure: Trigonal (microcrystalline/cryptocrystalline); Cleavage: None (fractures conchoidally); Specific gravity: 2.6-2.7

Hardness: 6
Color: Opaque yellow, tan, and earthy tones with iron inclusions
Luster: Waxy to dull

Identified June 21, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when silica-rich fluids permeate sedimentary layers or volcanic ash, replacing minerals or infilling cavities. Often found in nodules or bedded deposits within limestone or dolomite. Geological age varies widely from Precambrian to Cenozoic.

Uses & applications

Commonly used in lapidary work for jewelry and polishing, aggregate in construction, and historically used to create sharp stone tools like scrapers and arrowheads due to its conchoidal fracture.

Geological facts

Jasper is an impure variety of silica, with its yellow color usually attributed to goethite or other iron oxides. It has been used since antiquity as a gemstone and for ritualistic objects.

Field identification & locations

Identify by its waxy luster, smoothness to the touch, and distinct shell-like conchoidal fracture pattern. Found globally in riverbeds and sedimentary basins. Collectors should look for unique banding or color patterns.

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Sandstone or Siltstone

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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

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Sandstone

Arenite

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