sedimentary
Chalk
Calcium Carbonate (CaCO3)
Hardness: 2-3 (Mohs scale), Color: White to grey, Luster: Dull/Earthy, Structure: Microcrystalline/Amorphous, Density: 2.2-2.3 g/cm3
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 2-3 (Mohs scale), Color: White to grey, Luster: Dull/Earthy, Structure: Microcrystalline/Amorphous, Density: 2.2-2.3 g/cm3
Formation & geological history
Formed in deep marine environments from the accumulation of microscopic skeletal remains (coccospheres) of marine algae during the Cretaceous period.
Uses & applications
Used in agriculture for soil treatment, production of lime, construction material as Portland cement, and traditionally as a drawing instrument.
Geological facts
The word 'Cretaceous' comes from the Latin word 'creta' meaning chalk, reflecting the vast deposits formed during that era. The White Cliffs of Dover are the most famous example.
Field identification & locations
Identify by its soft texture, ability to leave a white streak on dark surfaces, and violent effervescence when exposed to dilute hydrochloric acid. Commonly found in coastal chalk landscapes.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary
Sandstone (with man-made markings)
Arenite (composed primarily of Quartz, SiO2)
sedimentary