sedimentary
Iron-rich chert or jasper
Microcrystalline quartz (SiO₂), likely hematite/goethite-bearing
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; dark gray to black with rusty orange-brown weathering, dull to waxy luster, and conchoidal fracture. The fine-grained quartz has no visible cleavage; iron oxides produce the ochre coloration.
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Physical properties
Hardness about 6.5–7 Mohs; dark gray to black with rusty orange-brown weathering, dull to waxy luster, and conchoidal fracture. The fine-grained quartz has no visible cleavage; iron oxides produce the ochre coloration.
Formation & geological history
Likely formed as chemically precipitated or replacement silica in ancient marine sediment, later stained or altered by oxidizing groundwater. Exact geological age cannot be determined from the photograph.
Uses & applications
Used historically for tools and occasionally as ornamental stone or lapidary material; attractive pieces may be polished, though this specimen appears common and rough.
Geological facts
Chert and jasper are varieties of microcrystalline quartz; red, orange, and brown colors commonly result from hematite or limonite/goethite.
Field identification & locations
Identify by its glassy-waxy appearance, very hard surface, and sharp conchoidal edges; it should scratch ordinary glass and resist a steel blade. Common in sedimentary formations, gravel beds, and iron-rich terrains worldwide.
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