sedimentary
Limestone with Secondary Mineralization
Calcium Carbonate (CaCO3)
Hardness: 3 (Mohs scale); Color: Gray to tan; Luster: Dull/Earthy; Crystal structure: Microcrystalline (calcite); Cleavage: Rhombohedral (microscopic); Specific gravity: 2.7
- Hardness
- 3 (Mohs scale)
- Color
- Gray to tan
- Luster
- Dull/Earthy
Identified More sedimentary →
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Physical properties
Hardness: 3 (Mohs scale); Color: Gray to tan; Luster: Dull/Earthy; Crystal structure: Microcrystalline (calcite); Cleavage: Rhombohedral (microscopic); Specific gravity: 2.7
Formation & geological history
Formed in marine environments through the accumulation of shell, coral, and algal debris. The tan areas represent secondary mineralization or oxidation occurring over millions of years (often Paleozoic to Mesozoic era).
Uses & applications
Limestone is used extensively in construction (aggregate, cement), manufacturing (steel flux), and agriculture (lime). This specific specimen is primarily of interest for educational collecting.
Geological facts
Limestone covers about 10% of the total surface area of the Earth's dry land. It is the primary rock found in the Pyramids of Giza.
Field identification & locations
Identify in the field by its reaction to dilute hydrochloric acid (it will fizz). Look for fossil fragments or smooth, fine-grained gray textures in road cuts and riverbeds.
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