According to Discovering Fossils, chalk occurs naturally in nature as calcium carbonate, a form of limestone. Limestone is formed from the decomposition and sedimentation of Coccolithophores skeletons, a type of plankton.Know More
Coccolithophores are chalk-forming plankton. They feature spherical skeletons called cocospheres, which are formed from calcareous discs called coccoliths. After death, the cocospheres and coccoliths settle down to the sea floor and decompose to their constituent parts. Over the years, the skeletons accumulate and form lime mud under the right conditions.
After geologic time has passed and sediments have started to build on top, sea water subsides, and the lime mud is subjected to tremendous heat and pressure. This removes the water and compacts the sediment layer into rock.
In order to manufacture slender sticks of chalk, limestone is first quarried. Next, the limestone is crushed by a jaw crusher. It is then wet-milled with water in a rotating steel drum with metal balls to crush the chalk further and wash away impurities. The chalk is then sifted over vibrating screens to separate large particles from the fine dust. It is then mixed with water, formed and cut to its proper length, and cured in an oven for four days.Learn more about States of Matter
Hydrogen does not exist in pure form in nature and instead is produced from a primary energy source, such as fossil fuels, solar, geothermal and wind energy, or extracted from other elements such as oxygen. Hydrogen is found embedded in, or coexisting with, other elements on Earth, in water and in the atmosphere. Hydrogen is quite abundant but is often difficult to extract and separate from surrounding minerals and elements.Full Answer >
In nature, nitrous oxide comes from the nitrogen cycle. This greenhouse gas also comes from the burning of oil products and the use of synthetic fertilizers.Full Answer >
The element lead has been known since ancient times and is sometimes found free in nature, but most lead on Earth is obtained by burning the ore galena in hot air. Today, lead is also obtained through the mining of ores such as minum, cerussite and anglesite.Full Answer >
According to About.com, mercury is rarely found on its own in nature. It is extracted from cinnabar, which is mercury(I) sulphide. The raw material is heated to vaporize the mercury, which is collected and contained in its liquid form.Full Answer >