sedimentary
Limestone (River Pebble)
Sedimentary Calcium Carbonate (CaCO3)
Hardness: 3 (Mohs scale); Color: Grayish-white; Luster: Dull to earthy; Texture: Fine-grained, smooth from water erosion; Cleavage: None/Irregular
- Hardness
- 3 (Mohs scale)
- Color
- Grayish-white
- Luster
- Dull to earthy
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Physical properties
Hardness: 3 (Mohs scale); Color: Grayish-white; Luster: Dull to earthy; Texture: Fine-grained, smooth from water erosion; Cleavage: None/Irregular
Formation & geological history
Formed through the accumulation of shell, coral, algal, and fecal debris in marine environments. This specific specimen has been shaped and smoothed by fluvial (river) or coastal water erosion.
Uses & applications
Common limestone is used in construction as aggregate, in cement manufacturing, and in agriculture as lime. Smooth pebbles like this are popular for landscaping, garden decoration, and as lucky stones.
Geological facts
Limestone accounts for about 10% of the total volume of all sedimentary rocks. It often contains fossils of microscopic marine organisms. Heart-shaped stones like this are common examples of naturally occurring water erosion.
Field identification & locations
Identify by its light color, soft texture (can be scratched by a steel knife), and effervescent reaction to dilute hydrochloric acid. Commonly found in riverbeds, lake shores, and coastal regions.
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