mineral

Quartz Pebble (with Manganese dendrites/staining)

Silicon Dioxide (SiO2) with Manganese Oxide impurities

Hardness: 7 (Mohs scale); Color: Milky white with black/grey dendritic staining; Luster: Vitreous to waxy (when river-worn); Crystal structure: Hexagonal (trigonal); Cleavage: None/Conchoidal fracture; Specific gravity: 2.65

Hardness: 7 (Mohs scale)
Color: Milky white with black/grey dendritic staining
Luster: Vitreous to waxy (when river-worn)

Identified April 22, 2026More mineral →

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Physical properties

Formation & geological history

Formed from hydrothermal veins or as a constituent in various rock types. This specific specimen has been smoothed by water erosion (river or beach) and displays surface staining or dendrites from iron/manganese minerals seeping into fractures over thousands of years.

Uses & applications

Common quartz is used in glassmaking, electronics (piezoelectric properties), abrasives, and as decorative river stones for landscaping.

Geological facts

The black markings are often mistaken for fossils or 'plant moss,' but they are actually inorganic metallic oxide minerals that crystallized into branching patterns or surface stains.

Field identification & locations

Identify in the field by its hardness (ability to scratch glass), milky translucency, and the presence of conchoidal (shell-like) fractures where it has chipped. Commonly found in riverbeds, glacial tills, and beaches worldwide.

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Mineral/Rock

Banded Gneiss (River Rock/Pebble)

Gneiss (specifically a banded variety often found as a river rock)

Metamorphic Rock

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mineral