sedimentary
Shale with Coprolite influence
Argillaceous sedimentary rock (Shale/Mudstone)
Hardness: 3 on Mohs scale; Color: Dark grey to brown; Luster: Dull or earthy; Structure: Fine-grained, fissile; Cleavage: Planar (along bedding planes); Specific Gravity: 2.4-2.8
- Hardness
- 3 on Mohs scale
- Color
- Dark grey to brown
- Luster
- Dull or earthy
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Physical properties
Hardness: 3 on Mohs scale; Color: Dark grey to brown; Luster: Dull or earthy; Structure: Fine-grained, fissile; Cleavage: Planar (along bedding planes); Specific Gravity: 2.4-2.8
Formation & geological history
Formed through the compaction of silt and clay-sized mineral particles over millions of years, often in slow-moving water like river deltas or lake beds. This specimen specifically shows signs of organic inclusion or concretion-like weathering.
Uses & applications
Primarily used in the manufacture of brick, pottery, tile, and Portland cement. Some organic-rich shales are sources of oil and natural gas.
Geological facts
Shale is the most common sedimentary rock on Earth, making up approximately 70 percent of the rocks in the crust. It often preserves fossils because of the fine-grained nature of the sediment.
Field identification & locations
Identify in the field by its fine layers and ease of breaking into flat fragments. Look for it in areas with historical water deposition. Collectors should check for fossil imprints within the layers.
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