sedimentary
Chert (Yellow Jasper)
Microcrystalline Quartz (SiO2)
AI-generated identification · may be incorrectMohs hardness of 6.5-7. Opaque to translucent. Waxy to dull luster. Conchoidal (shell-like) fracture. Trigonal crystal system. Specific gravity of 2.6-2.7. Color is yellowish-brown due to iron oxide inclusions.
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Physical properties
Mohs hardness of 6.5-7. Opaque to translucent. Waxy to dull luster. Conchoidal (shell-like) fracture. Trigonal crystal system. Specific gravity of 2.6-2.7. Color is yellowish-brown due to iron oxide inclusions.
Formation & geological history
Formed by the precipitation of silica from groundwater or within deep-sea marine sediments. This microcrystalline variety often forms as nodules or bedded deposits within limestone or sandstone formations.
Uses & applications
Historically used for making stone tools (arrowheads). Modern uses include tumbled stones for jewelry, lapidary art, and aquarium decor due to its chemical stability.
Geological facts
Jasper and chert have been used by humans for over a million years to create sharp-edged tools. Yellow jasper is specifically associated with various folklore traditions as a stone of protection and solar energy.
Field identification & locations
Identify in the field by its hardness (scratches glass), waxy feel, and smooth curved (conchoidal) breaks. Often found in riverbeds or coastal deposits.
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