Is chalk a compound, element, or mixture?
Chalk is a soft, white, porous, sedimentary carbonate rock, a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of sub-microscopic plankton.In Western Europe, chalk 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.
For raising pH in soils with high acidity, chalk is mined for use in industry, such as for quicklime, bricks and builder's putty.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.
Between 99 and 65 million years ago, chalk was formed.The chalk downland of Northern Europe was oozing at the bottom of the sea ninety million years ago.When it was studied under the microscope, chalk was found to be composed almost entirely of coccoliths.The rich seawater was used to make their shells.As they died, a substantial layer gradually built up over millions of years and eventually became rock.These former sea-floor deposits were raised above sea level by the formation of the European Alps.There is a citation needed.
It forms from the gradual accumulating of minute calcite shells of single-celled marine animals known as foraminifera, as well as larger ostracods and bivalves.The foraminifera fall to the sea floor and are compressed into chalk rock.There is a citation needed.
There is a type of limestone called chalk.Calcite is an ionic salt.There is a citation needed.
The chalk has minor amounts of silt and clay.While chalk is similar in appearance to gypsum and diatomite, it is different in many ways.[4]
It is unusual to see chalk in the thickness of the beds in Western Europe.Most cliffs of chalk don't have any obvious bedding planes, unlike thick sequence of limestone such as the Carboniferous Limestone.This could mean very stable conditions for tens of millions of years.There is a citation needed.
There are bands parallel to the bedding that are embedded in chalk.It is most likely derived from sponge spicules or other siliceous organisms.It is deposited around larger fossils such as Echinoidea.The molecule was replaced by flint.There is a citation needed.
The cliffs formed by chalk ridges meet the sea and are taller than the clays with which they are associated.A scarp slope is formed when bands of chalk reach the surface at an angle.A large amount of ground water can be held by chalk because it is well jointed.There is a citation needed.
The Chalk Group was deposited during the late Cretaceous Period.The White Cliffs of Dover are in Kent, England, as well as the Cap Blanc Nez on the other side of the Dover Strait.Artificial caves are used for wine storage in the Champagne region of France.The highest chalk cliffs in the world can be found at Jasmund National Park in Germany and at Mns Klint in Denmark.There is a citation needed.
Above ground and underground chalk deposits are mined.Chalk products such as quicklime and bricks were in high demand during the Industrial Revolution.There are some abandoned chalk mines that are still tourist destinations.There is a citation needed.
Most people first encounter chalk in school where it refers to blackboard chalk, which was originally made of mineral chalk and leaves particles that stick to rough surfaces, allowing it to make writing that can be easily erased.Mineral chalk, other mineral sources of calcium carbonate, or the mineral gypsum can now be used by chalk manufacturers.While gypsum-based blackboard chalk is the lowest cost to produce and widely used in the developing world, use of carbonate- based chalk produces larger particles and thus less dust, and it is marketed as "dustless chalk".[5]
The calcium carbonate chalk used to draw on the sidewalks, streets, and driveway is mostly made of gypsum.[6]
Slaked lime is a source of quicklime from thermal decomposition.Deneholes are an example of ancient chalk pits.The sites of ancient flint mines may be marked by bell pits.The surface remains at Cissbury are one example, but perhaps the most famous is the complex at Grimes Graves in Norfolk.