mineral
Quartz Pebble (Chalcedony / River Pebble)
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness 7 on Mohs scale, waxy to vitreous luster, cryptocrystalline or microcrystalline quartz structure, yellowish-brown to tan color, highly rounded and smooth.
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Physical properties
Hardness 7 on Mohs scale, waxy to vitreous luster, cryptocrystalline or microcrystalline quartz structure, yellowish-brown to tan color, highly rounded and smooth.
Formation & geological history
Formed via silica precipitation in sedimentary or volcanic cavities, subsequently weathered and mechanically rounded by river or coastal fluvial action.
Uses & applications
Commonly used in landscaping, tumbling, decorative aggregate, or polished for casual jewelry and craft pieces.
Geological facts
Water-worn quartz pebbles are extremely durable, surviving extensive sedimentary transport that breaks down softer surrounding rocks.
Field identification & locations
Identified by its high hardness (scratches glass), lack of visible cleavage, smooth rounded contours, and translucent edges. Abundant in stream beds, coastlines, and alluvium across coastal Brazil (Paraíba region).
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Other mineral specimens
Gneiss or Schist
Gneiss or Mica Schist with Garnet
Metamorphic
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Pegmatite with Tourmaline and Quartz
Igneous Pegmatite
igneous
Granite
Granite (Phaneritic intrusive igneous rock)
igneous
Septarian Pebble
Septarian nodule / Concretion
sedimentary