**1. Chalk Composition and Formation:**
– Chalk is a fine-textured, light-colored limestone composed of tiny calcite shell fragments of plankton like foraminifera or coccolithophores.
– It contains larger fragments of intact plankton skeletons and skeletal fragments of organisms like molluscs.
– Typically almost pure calcite with 2-4% other minerals like quartz and clay.
– Chalk formed in Late Cretaceous and early Palaeocene Epochs, 100-61 million years ago, on continental shelves at depths of 100-600 meters.
– Formed from low-magnesium calcite skeletons of microscopic organisms, showing signs of compaction and often containing flint bands or nodules.
– Chalk deposits can be hundreds of meters thick and are closely linked to the carbon cycle.
**2. Geographic Distribution and Mining:**
– Chalk is common in Cretaceous marine beds, with notable locations in Europe like the White Cliffs of Dover and Champagne region.
– High chalk cliffs are found in various places like Jasmund National Park and Møns Klint, as well as in North America, Egypt, Australia, Cyprus, and under the Pacific Ocean.
– Chalk is mined from deposits above and underground, with mining having boomed during the Industrial Revolution for products like quicklime.
– Chalk mining is an important industry for various commercial applications.
**3. Industrial and Commercial Uses:**
– Chalk is used in various applications such as school blackboard chalk, glazing putty, quicklime production, agriculture, cleaning products, toothpaste, and fine metal polishing.
– It is also used in field sports like tennis for marking boundaries, in gymnastics, rock-climbing, weightlifting, and tug of war to reduce slipping, and in house construction as a building material.
– Chalk has been used historically in fingerprint powder (with mercury, discontinued due to toxicity) and in some houses as the main building material.
**4. Geological Significance and Studies:**
– Chalk formations are important geological records of past marine environments and can provide insights into ancient climates and ecosystems.
– The study of sedimentology, stratigraphy, taphonomy, and ichnology of chalk contributes to understanding prehistoric environments and resources.
– Chalk reservoirs in regions like the North Sea and the Dutch North Sea are of particular interest for geological research and evaluation of resources.
**5. Manufacturing and Processing:**
– Chalk’s surface and colloidal properties, along with its use in products like glazing putty, rubber, and toothpaste, are subjects of manufacturing and processing studies.
– The process of making chalk, calcium carbonate properties, and the estimation of talc properties after milling are key areas of focus for researchers and manufacturers.
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. Chalk is common throughout Western Europe, where deposits underlie parts of France, and steep cliffs are often seen where they meet the sea in places such as the Dover cliffs on the Kent coast of the English Channel.
| Sedimentary rock | |
 Beachy Head is a part of the extensive Southern England Chalk Formation. | |
| Composition | |
|---|---|
| Calcite (calcium carbonate) |
Chalk is mined for use in industry, such as for quicklime, bricks and builder's putty, and in agriculture, for raising pH in soils with high acidity. It is also used for "blackboard chalk" for writing and drawing on various types of surfaces, although these can also be manufactured from other carbonate-based minerals, or gypsum.