metamorphic
Weathered quartz-rich pebble, likely sandstone or quartzite
Quartzite (SiO₂), possibly ferruginous sandstone
AI-generated identification · may be incorrectTan, fine-grained, dull to weakly earthy luster, rounded by transport and weathering; chiefly quartz with iron-oxide staining. Quartzite has Mohs hardness ~7, no cleavage, conchoidal to irregular fracture, and specific gravity ~2.65; the image cannot confirm grain cementation.
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Physical properties
Tan, fine-grained, dull to weakly earthy luster, rounded by transport and weathering; chiefly quartz with iron-oxide staining. Quartzite has Mohs hardness ~7, no cleavage, conchoidal to irregular fracture, and specific gravity ~2.65; the image cannot confirm grain cementation.
Formation & geological history
If quartzite, it formed when quartz sandstone recrystallized under low- to medium-grade metamorphism, commonly during Precambrian–Paleozoic mountain building. If sandstone, it is a sedimentary rock formed from cemented sand and later weathered into a pebble.
Uses & applications
Commonly used as aggregate, road stone, landscaping material, and building stone; attractive pieces may be collected but are generally not gem-grade.
Geological facts
The rounded shape indicates abrasion in a stream, beach, or glacial environment. Dark branching marks may be iron-oxide veins, manganese staining, or surface weathering rather than fossils.
Field identification & locations
Scratch-testing with a steel nail helps: quartzite should resist scratching, while sandstone may shed grains. A fresh broken surface revealing fused quartz grains supports quartzite; common sources include stream gravels and quartzite-bearing uplands worldwide.
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