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- Chalk is a soft, white, porous, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor.
en.wikipedia.org/wiki/Chalk
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Chalk is a fine-textured, earthy type of limestone distinguished by its light colour, softness, and high porosity. [1][2] It is composed mostly of tiny fragments of the calcite shells or skeletons of plankton, such as foraminifera or coccolithophores. [1]
Oct 10, 2023 · Upper Cretaceous deposits of pure and bright white sedimentary chalk along the coast of central southern Cyprus. Chalk rock is a distinctive type of sedimentary rock that forms through a specific process and is primarily composed of the mineral calcite (calcium carbonate).
Background. Chalk used in school classrooms comes in slender sticks approximately .35 of an inch (nine millimeters) in diameter and 3.15 inches (80 millimeters) long. Lessons are often presented to entire classes on chalk-boards (or blackboards, as they were originally called) using sticks of chalk because this method has proven cheap and easy.
Aug 10, 2024 · chalk, soft, fine-grained, easily pulverized, white-to-grayish variety of limestone. Chalk is composed of the shells of such minute marine organisms as foraminifera, coccoliths, and rhabdoliths. The purest varieties contain up to 99 percent calcium carbonate in the form of the mineral calcite.
- The Editors of Encyclopaedia Britannica
Images by the United States Geological Survey. How Does Chalk Form? Chalk forms from a fine-grained marine sediment known as ooze. When foraminifera, marine algae, or other organisms living on the bottom or in the waters above die, their remains sink to the bottom and accumulate as ooze.
Chalk is found throughout much of northwestern Europe. England’s famous white cliffs of Dover are made from chalk. In the United States, chalk deposits are found in Arkansas, Louisiana, Texas, and Wyoming.
Dec 1, 2007 · Chalk is a sedimentary rock of unusually high homogeneity on the scale where physical properties are measured, but the properties fall in wide ranges. Chalk may thus be seen as the ideal...
