sedimentary

Limestone (specifically Fossiliferous Limestone)

Calcium Carbonate (CaCO3)

AI-generated identification · may be incorrect

Hardness: 3 on Mohs scale; Color: Gray to light tan; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.5–2.7

Hardness: 3 on Mohs scale
Color: Gray to light tan
Luster: Dull to earthy

Identified April 9, 2026More sedimentary →

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Physical properties

Hardness: 3 on Mohs scale; Color: Gray to light tan; Luster: Dull to earthy; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.5–2.7

Formation & geological history

Formed in warm, shallow marine environments through the accumulation of skeletal fragments of marine organisms like coral, foraminifera, and mollusks over millions of years.

Uses & applications

Used primarily in construction (as aggregate and concrete base), road building, production of cement, soil conditioner in agriculture, and as a dimension stone for architectural accents.

Geological facts

Limestone makes up about 10% of the total volume of all sedimentary rocks. Most of the world's great caves are carved out of limestone by the acidic nature of groundwater.

Field identification & locations

Identify in the field by checking for fossil inclusions and performing an ‘acid test’ (it will effervesce when exposed to weak hydrochloric acid or vinegar). Commonly found in riverbeds and areas that were ancient seabeds.