sedimentary
Brown chert or jasper pebble
Microcrystalline quartz (SiO₂), likely iron-oxide-bearing chert/jasper
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; opaque brown-orange color with white weathering or quartz veining, dull to waxy luster, and no visible cleavage. Very fine-grained cryptocrystalline quartz; specific gravity about 2.6.
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Physical properties
Hardness about 6.5–7 Mohs; opaque brown-orange color with white weathering or quartz veining, dull to waxy luster, and no visible cleavage. Very fine-grained cryptocrystalline quartz; specific gravity about 2.6.
Formation & geological history
Forms when silica-rich fluids replace or cement sediment, commonly in marine or volcanic sedimentary environments; iron oxides produce the brown-red color. Its exact age cannot be determined from the photograph.
Uses & applications
Used as decorative stone, lapidary material, beads, cabochons, and occasionally toolstone; this small irregular specimen has minimal commercial value.
Geological facts
Chert and jasper are varieties of microcrystalline quartz, distinguished mainly by opacity and impurities. White patches may represent quartz, weathering, or a superficial mineral coating.
Field identification & locations
Commonly found as resistant rounded pebbles in stream gravels, beaches, and sedimentary formations; a glassy edge, lack of cleavage, and ability to scratch glass support identification. Acid will not normally fizz.
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