sedimentary
Brown Jasper / Chert
Microcrystalline Quartz (SiO2)
Mohs hardness of 6.5-7; waxy to vitreous luster when wet or polished; cryptocrystalline structure; brownish-yellow to dark yellowish-brown color with internal micro-fractures and mottling; conchoidal fracture.
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Physical properties
Mohs hardness of 6.5-7; waxy to vitreous luster when wet or polished; cryptocrystalline structure; brownish-yellow to dark yellowish-brown color with internal micro-fractures and mottling; conchoidal fracture.
Formation & geological history
Formed through the precipitation of silica-rich solutions or the recrystallization of radiolarian/diatomaceous ooze in marine or sedimentary environments.
Uses & applications
Used in lapidary arts, tumbled rock collecting, decorative crafts, and historical tool-making (flint knapping).
Geological facts
Jasper and chert are opaque forms of microcrystalline quartz; the distinct brown hues are usually caused by iron oxide impurities such as goethite or limonite.
Field identification & locations
Identified by its smoothness, hardness (will scratch glass), conchoidal fracture, and opaque brownish coloration. Commonly found in riverbeds, gravel pits, and shoreline beaches.
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