sedimentary

Limestone with Secondary Mineralization

Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

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 June 26, 2026More 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.