sedimentary
Limestone Pebble
Limestone (Calcium Carbonate - CaCO3)
Hardness: 3 on Mohs scale; Color: light gray to off-white; Luster: dull/earthy; Structure: microcrystalline; Cleavage: none; Specific Gravity: 2.5-2.7
- Hardness
- 3 on Mohs scale
- Color
- light gray to off-white
- Luster
- dull/earthy
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Physical properties
Hardness: 3 on Mohs scale; Color: light gray to off-white; Luster: dull/earthy; Structure: microcrystalline; Cleavage: none; Specific Gravity: 2.5-2.7
Formation & geological history
Formed in clear, warm, shallow marine waters through the accumulation of shell, coral, algal, and fecal debris. This specimen has been rounded and smoothed by water erosion.
Uses & applications
Commonly used as aggregate for cement, road base, or in aquariums and landscaping. High-purity limestone is used in glass making and agriculture.
Geological facts
Limestone makes up about 10% of the total volume of all sedimentary rocks on Earth. This specific pebble shape, known as a 'clast', indicates it has spent significant time in a high-energy water environment like a beach or riverbed.
Field identification & locations
Identify in the field by its softness (can be scratched by a steel nail) and its reaction to dilute hydrochloric acid (it will fizz/effervesce).
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