sedimentary

Veined Pebble (Septarian or Quartz-Veined Chert/Basalt)

Silicon Dioxide (SiO2) veins in matrix

Hardness: 6.5 to 7 on the Mohs scale (quartz component); Color: Dark brown to reddish-black matrix with crisscrossing white-to-pinkish quartz/calcite veins; Luster: Vitreous to dull when wet; Structure: Microcrystalline with fracture-filling veinlets.

Hardness: 6
Luster: Vitreous to dull when wet

Identified July 23, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through hydrothermal fluid precipitation filling fractures (joints or septarian cracks) in a host rock like chert, basalt, or mudstone, subsequently rounded and smoothed by beach wave or stream action.

Uses & applications

Primarily collected as decorative beach pebbles, landscaping stone, or lapidary tumbling material.

Geological facts

The distinctive crisscrossing patterns are formed when tectonic stress or shrinkage causes cracking in the parent rock, allowing mineral-rich water to deposit quartz or calcite inside the fractures before erosion shapes the pebble.

Field identification & locations

Look for a smooth, water-worn beach pebble featuring lighter-colored, hard raised veins that stand out against a darker fine-grained matrix. Found along gravel beaches, riverbeds, and glacial deposits globally.

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