metamorphic

Weathered quartz-rich rock, likely quartzite

Quartzite (mostly crystalline SiO₂), tentative identification

AI-generated identification · may be incorrect

Tan to brown, opaque, dull-to-slightly waxy luster, irregular fracture, and a fine granular texture. Quartzite is typically Mohs 7, with no cleavage; the apparent pale patches may be quartz-rich areas or weathering rather than distinct crystals.

Identified September 19, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when quartz-rich sandstone was recrystallized under heat and pressure, commonly during regional metamorphism. Its precise geological age cannot be determined from the photograph; regional bedrock near 17.9°S, 51.7°W includes sedimentary and weathered continental rocks, making quartz-rich material plausible.

Uses & applications

Used as aggregate, road stone, building stone, and decorative slabs; attractive pieces may be collected, though this small irregular specimen has little commercial value.

Geological facts

Quartzite commonly breaks across grains rather than around them, unlike weak sandstone. Iron-oxide staining can produce tan, orange, or reddish-brown colors.

Field identification & locations

Likely identification requires a fresh-break test: a steel file should not scratch true quartzite, while the rock may scratch glass. A hand lens showing fused interlocking quartz grains would support the diagnosis; a gritty, easily friable texture would favor sandstone or silicified sediment.