sedimentary

Chalk

Micrite (primarily Calcium Carbonate or CaCO3)

AI-generated identification · may be incorrect

Hardness: 1-3 on Mohs scale; Color: White to grey/buff; Luster: Dull/Earthy; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.3-2.6

Hardness: 1-3 on Mohs scale
Color: White to grey/buff
Luster: Dull/Earthy

Identified June 28, 2026More sedimentary →

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Physical properties

Hardness: 1-3 on Mohs scale; Color: White to grey/buff; Luster: Dull/Earthy; Crystal Structure: Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.3-2.6

Formation & geological history

Formed from the accumulation of microscopic marine organisms like coccolithophores on the ocean floor, primarily during the Cretaceous period.

Uses & applications

Used in the manufacturing of cement, lime, fertilizer, blackboard chalk, and as a whitener in toothpaste and paper production.

Geological facts

The famous White Cliffs of Dover in England are made almost entirely of chalk, consisting of trillions of microscopic skeletons from marine algae.

Field identification & locations

Identify by its soft, powdery texture and high reactivity to cold dilute hydrochloric acid (it will fizz strongly). Found in deep marine depositional environments worldwide.