metamorphic
Rounded yellow-brown quartzite or quartz pebble
Quartzite, predominantly SiO₂
AI-generated identification · may be incorrectSmall, water-worn pebble with ochre-yellow coloration, dull to slightly waxy luster, and no visible cleavage. Quartzite typically has Mohs hardness 7, granular interlocking quartz, and specific gravity about 2.6–2.7; iron-oxide staining likely causes the color.
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Physical properties
Small, water-worn pebble with ochre-yellow coloration, dull to slightly waxy luster, and no visible cleavage. Quartzite typically has Mohs hardness 7, granular interlocking quartz, and specific gravity about 2.6–2.7; iron-oxide staining likely causes the color.
Formation & geological history
Probably a weathered and transported quartz-rich metamorphic fragment, formed when sandstone recrystallized under heat and pressure. The coarse location near 18.2°S, 47.9°W in central Brazil is compatible with abundant Precambrian quartz-rich rocks and alluvial pebbles.
Uses & applications
Commonly used as aggregate, road stone, landscaping material, and occasionally decorative stone; this small rounded piece has little commercial value.
Geological facts
The image cannot distinguish quartzite confidently from chert, chalcedony, or a strongly iron-stained quartz pebble. A steel knife should not scratch it, while quartzite may scratch ordinary glass.
Field identification & locations
Likely found in stream or soil gravel. Look for a sugary granular texture and consistent hardness; a glassy, waxy fracture would favor chalcedony/chert. A streak test, hardness test, and fresh broken surface would improve identification.
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