metamorphic
Slate River Stone
Foliated Metamorphic Rock (composed of illite, chlorite, and quartz)
Hardness: 2.5-4 (Mohs); Color: Bluish-gray to dark gray; Luster: Dull to satiny; Crystal Structure: Microcrystalline; Cleavage: Perfect slaty cleavage; Specific Gravity: 2.7-2.8
- Hardness
- 2
- Color
- Bluish-gray to dark gray
- Luster
- Dull to satiny
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Physical properties
Hardness: 2.5-4 (Mohs); Color: Bluish-gray to dark gray; Luster: Dull to satiny; Crystal Structure: Microcrystalline; Cleavage: Perfect slaty cleavage; Specific Gravity: 2.7-2.8
Formation & geological history
Formed through low-grade metamorphism of shale or mudstone under relatively low pressure and temperature. This specimen has been smoothed and rounded by river or beach water erosion over thousands of years.
Uses & applications
Commonly used for flooring, roofing, pool tables, and garden landscaping. High-quality smooth stones are popular for decorative rock painting or as 'worry stones'.
Geological facts
Slate can be split into thin, durable sheets due to its slaty cleavage. It was historically used for blackboards and writing tablets before paper became cheap and widely available.
Field identification & locations
Identify in the field by its fine-grained texture and ability to split into thin sheets. This specific pebble shape is found in high-energy riverbeds or coastal rocky beaches. Look for its characteristic dull gray sheen and smooth, waxy feel when polished by water.
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