Q:

Where does chalk come from?

A:

Quick Answer

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.

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Where does chalk come from?
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Full Answer

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.

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Related Questions

  • Q:

    What is the chemical formula for chalk?

    A:

    The most common chemical formulas for chalk are CaCO3 (calcium carbonate) and CaO (calcium oxide). Chalk is a soft, porous sedimentary rock that is a form of limestone and is mainly composed of calcite (calcium carbonate).

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  • Q:

    What is chalk made from?

    A:

    Blackboard and sidewalk chalk can be made from either calcium carbonate (CaCO3) or calcium sulfate, also known as gypsum (CaSO4. Calcium carbonate is formed by the slow underwater compression and accumulation of the calcite shells of single-celled animals called coccolithophores. Gypsum is found in the form of sedimentary rock in evaporite beds and is deposited by sea and lake waters, hot-water springs and volcanic vapors.

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  • Q:

    What is the reaction between chalk and vinegar?

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    The reaction between chalk and vinegar is a neutralization reaction between calcium carbonate and acetic acid to produce water, carbon dioxide and calcium acetate. Carbon dioxide is a gas that causes the reaction to bubble.

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  • Q:

    What is the chemical formula for marble?

    A:

    Marble is made of calcium carbonate, CaCO3, which is also what limestone is made from. The only difference between limestone and marble is the crystalline structure. Limestone crystals are much smaller than that of marble, and limestone is much more porous.

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