sedimentary
Tumbled jasper or chert pebble
Microcrystalline quartz (SiO₂), likely iron-bearing jasper/chert
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; opaque gray-brown with reddish patches, waxy to dull luster, and no visible cleavage. The rounded shape and smooth surface indicate natural abrasion or tumbling.
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Physical properties
Hardness about 6.5–7 Mohs; opaque gray-brown with reddish patches, waxy to dull luster, and no visible cleavage. The rounded shape and smooth surface indicate natural abrasion or tumbling.
Formation & geological history
Silica-rich sediment or replacement material formed when cryptocrystalline quartz cemented or replaced sediments, commonly in ancient marine or volcanic environments. Its exact geological age cannot be determined from the photograph.
Uses & applications
Used as an inexpensive lapidary stone for cabochons, beads, carvings, and polished or tumbled specimens; occasionally used decoratively.
Geological facts
Jasper is an opaque variety of chalcedony, while chert is the broader fine-grained silica category; the boundary between them is often descriptive rather than strict.
Field identification & locations
Look for glassy-to-waxy luster, very fine grain, opacity, and resistance to scratching; it should scratch ordinary glass but not be scratched by a steel knife. Common worldwide, especially in sedimentary and volcanic terrains.
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