metamorphic
Stiped Slate Beach Pebble
Low-grade Metamorphic Slate with Quartz Vein (SiO2 on Phyllosilicate base)
Hardness: 2.5–4.0 for host rock, 7 for vein; Color: Grey to bluish-grey with white banding; Luster: Dull/Waxy; Structure: Foliated; Slates have fine-grained texture and perfect cleavage.
- Hardness
- 2
- Color
- Grey to bluish-grey with white banding
- Luster
- Dull/Waxy
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Physical properties
Hardness: 2.5–4.0 for host rock, 7 for vein; Color: Grey to bluish-grey with white banding; Luster: Dull/Waxy; Structure: Foliated; Slates have fine-grained texture and perfect cleavage.
Formation & geological history
Formed through the regional metamorphism of shale or mudstone under low heat and pressure. The white stripe is a 'hydrothermal vein' formed when silica-rich water filled a fracture in the rock and crystallized as mineral quartz.
Uses & applications
Used historically for roofing slates and writing tablets. Polished pebbles are used for garden landscaping, aquarium decor, and pocket 'worry stones'.
Geological facts
The white line is often called a 'Wishing Line' in folklore. If the line circles the stone completely without breaking, it is considered a lucky 'Wishing Stone' by beachcombers.
Field identification & locations
Identify by its flat, smooth texture and the distinct perpendicular quartz band. Commonly found on high-energy beaches in the UK (Cornwall), New England, and the Pacific Northwest.
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