mineral

Iron-stained Quartz / Chalcedony Pebble

Silicon Dioxide (SiO2) with Iron Oxide inclusions

Hardness: 7 on Mohs scale. Color: Translucent yellowish-orange, honey-brown to reddish, caused by iron oxides. Luster: Waxy to vitreous. Crystal Structure: Microcrystalline or trigonal quartz. Cleavage: None (conchoidal fracture). Specific Gravity: 2.6-2.65.

Hardness: 7 on Mohs scale
Luster: Waxy to vitreous

Identified July 27, 2026More mineral →

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Physical properties

Formation & geological history

Formed via secondary silica deposition in volcanic cavities, sedimentary beds, or hydrothermal veins. Subsequent erosion and water action stream-rounded the specimen into a pebble, while iron oxide stains developed within fractures and surface layers.

Uses & applications

Commonly used for lapidary work, tumbling, decorative landscaping, and by beginner rockhounds for collecting.

Geological facts

Yellow to orange-brown varieties of microcrystalline quartz are often called carnelian or sard when uniform, or simply iron-stained quartz pebbles when naturally weathered in rivers and beaches.

Field identification & locations

Identified by its waxy-to-glassy sheen, translucency, rounded smooth edges, and scratch resistance to standard steel. Commonly found in gravel bars, riverbeds, beaches, and glacial till.

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Septarian Pebble

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sedimentary

Potassium Feldspar (Orthoclase)

Orthoclase (KAlSi3O8)

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