mineral

Likely tumbled milky quartz

Quartz (silicon dioxide, SiO₂)

AI-generated identification · may be incorrect

Small, rounded, cream-white translucent pebble with a slightly glossy surface; fine details are blurred. Quartz has Mohs hardness 7, a vitreous luster, hexagonal crystal structure, and no cleavage, breaking with conchoidal fracture.

Identified September 26, 2026More mineral →

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Physical properties

Formation & geological history

Quartz forms in many igneous, metamorphic, and sedimentary settings, commonly crystallizing from silica-rich fluids; its age cannot be determined from the photo. The smooth shape suggests natural abrasion or tumbling/polishing.

Uses & applications

Used in jewelry and decorative objects; quartz is also important in glassmaking and electronics.

Geological facts

Quartz is one of Earth’s most abundant minerals and resists weathering, so it commonly survives as rounded pebbles.

Field identification & locations

A scratch test against glass (quartz should scratch it) and conchoidal fracture can help distinguish quartz from softer lookalikes. Quartz is plausible near Rio de Janeiro, but the photo alone cannot confirm the local source or whether this was polished.