sedimentary

Gravel / Limestone Fragment

Calcium Carbonate (CaCO3) / Fine-grained Sedimentary Rock

AI-generated identification · may be incorrect

Hardness: 3-4 on Mohs scale. Color: Dull gray to charcoal with light flecks. Luster: Earthy to sub-vitreous. Fracture: Irregular to sub-conchoidal.

Hardness: 3-4 on Mohs scale
Color: Dull gray to charcoal with light flecks
Luster: Earthy to sub-vitreous

Identified July 24, 2026More sedimentary →

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Physical properties

Hardness: 3-4 on Mohs scale. Color: Dull gray to charcoal with light flecks. Luster: Earthy to sub-vitreous. Fracture: Irregular to sub-conchoidal.

Formation & geological history

Formed from the accumulation and compaction of organic debris, marine organism shells, or mineral precipitation in shallow aquatic environments over millions of years.

Uses & applications

Commonly crushed for construction aggregate, road base material, concrete production, and landscape graveling.

Geological facts

Limestone and related gravel rocks cover about 10% of the Earth's total sedimentary rock volume and often contain tiny microfossils.

Field identification & locations

Can be identified in the field by reacting (effervescing) with dilute hydrochloric acid or vinegar. Found abundantly in riverbeds, quarries, and gravel driveways.