Chalk
Rock made of calcite
Common
A soft, white, porous limestone made of the calcite plates of microscopic plankton. It forms the White Cliffs of Dover and Cap Blanc-Nez across the Channel, and underlies most of Champagne; flint grows in bands and nodules inside it.
Rock
- Kind of rock
- Chemical sedimentary rock
- Rock family
- Limestone and chalk
- Texture
- fine-grained, porous
- Shapes the land into
- Cliff
- How it forms
- The hard parts of plankton (foraminifera, coccolithophores) settle on the sea floor and harden; the European Chalk was laid down in the Late Cretaceous.
- Uses
- Quicklime, bricks, builder’s putty and cement, liming acid soils, and writing chalk; ancient pits were dug to reach its flint.
Crystallography
- Habits
- Earthy, Massive
Physical properties
- Luster
- Earthy, Dull
- Colors
- white
- Transparency
- Opaque
Geology
- Origins
- Sedimentary
- Geography
- England (White Cliffs of Dover), France (Cap Blanc-Nez, Champagne)
Classification
- Rarity
- Common
- Gem quality
- No
Sources
- Chalk. Wikipedia.
- C. R. Hallsworth, R. W. O’B. Knox, BGS Rock Classification Scheme, Volume 3: Classification of sediments and sedimentary rocks (Research Report RR 99-03). British Geological Survey, 1999.
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