sedimentary
Rounded quartz-rich pebbles, likely jasper/chert with one iron-stained specimen
Microcrystalline quartz (SiO₂), possibly jasper or chert; exact identification is uncertain from the image
AI-generated identification · may be incorrectSmall water-worn pebbles, mostly dark gray to brown with mottled pale patches and dull-to-waxy luster; one is orange-red, probably iron-oxide-stained quartz or jasper. Quartz hardness is about 7 Mohs, with no obvious cleavage and conchoidal fracture; density is typically 2.55–2.70 g/cm³.
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Physical properties
Small water-worn pebbles, mostly dark gray to brown with mottled pale patches and dull-to-waxy luster; one is orange-red, probably iron-oxide-stained quartz or jasper. Quartz hardness is about 7 Mohs, with no obvious cleavage and conchoidal fracture; density is typically 2.55–2.70 g/cm³.
Formation & geological history
Likely erosion and stream or gravel-bed transport of siliceous rock, followed by natural rounding. Chert and jasper commonly formed by silica replacement or precipitation in sedimentary environments, generally Precambrian to younger.
Uses & applications
Suitable for curiosities, tumbling, lapidary cabochons, and decorative aggregate; quality jasper may be used in jewelry. These small, ordinary pebbles have little commercial value.
Geological facts
The orange-red color commonly comes from hematite or goethite. Dark surfaces may also represent weathered basalt, but the mottled appearance favors chert/jasper; a close test is needed.
Field identification & locations
Near 20.1°S, 28.6°E, transported siliceous pebbles are plausible. Test streak, hardness, and fracture: quartz-rich pieces should scratch glass and show a white streak; basalt is usually heavier, uniformly fine-grained, and does not readily scratch glass.
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