metamorphic
Veined Pebble (Quartz/Calcite Veined Metamorphic/Sedimentary Rock)
Quartz / Calcite Veined Fault Breccia or Metamorphic Pebble
Hardness: 3-7 (varies by host rock vs. vein mineral). Color: Dark grey to black matrix with white to off-white mineral veins. Luster: Dull to vitreous. Texture: Fine-grained matrix cut by cross-cutting quartz or calcite veinlets. Specific Gravity: ~2.6-2.8.
- Hardness
- 3-7 (varies by host rock vs
- Luster
- Dull to vitreous
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Physical properties
Hardness: 3-7 (varies by host rock vs. vein mineral). Color: Dark grey to black matrix with white to off-white mineral veins. Luster: Dull to vitreous. Texture: Fine-grained matrix cut by cross-cutting quartz or calcite veinlets. Specific Gravity: ~2.6-2.8.
Formation & geological history
Formed when tectonic stress caused micro-fractures within a fine-grained host rock (such as slate, argillite, or mudstone). Hydrothermal fluids rich in silica (quartz) or calcium carbonate (calcite) precipitated inside the fractures, sealing them into distinct white veins. The rock was subsequently weathered and rounded into a river or beach pebble by water erosion.
Uses & applications
Decorative stones, educational specimens, landscaping pebble, and hand-carried 'worry stones' or wishing stones.
Geological facts
Small pebbles featuring distinct, continuous white rings or bands wrapping completely around them are often called 'Wishing Stones' in folklore, said to bring good luck when thrown into water.
Field identification & locations
Identify in the field by looking for smooth, water-worn pebbles featuring crisp, cross-cutting white lines traversing dark matrix rock. Quartz veins will scratch glass (Mohs 7), whereas calcite veins will react with dilute acid and scratch with a copper penny (Mohs 3). Common along gravel bars, riverbeds, and ocean beaches worldwide.
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