The Chemistry of Chalk

What is chalk?

‘calx’ the Latin word of Chalk. We get chalk from limestone. Most of the chalk we find today was made almost 60 to 100 million years ago. It is chemically made of calcium carbonate. This soft white porous sedimentary rock occurs naturally deep under the sea starts here, where small circular calcite plates called coccoliths accumulate to form limestone.

The natural form of chalk can be found in colors ranging from grey, white and yellow. Due to the different impurities in the chalk colors occurs accordingly.

Use of chalk

Chalk is pressed into white sticks which are then used for a variety of purposes from scribbling on the blackboard, outlining designs on fabrics for tailors and making art on pavements. Some of the different uses of chalk like blackboard chalk which is made from gypsum; sidewalk chalk, agriculture chalk made from calcium carbonate and calcium oxide.

‘The Chemistry of Chalk’ also has a variety of other uses; mostly used to draw those white lines that define the court boundaries in sports like tennis, badminton and other such sports. ‘The Chemistry of Chalk’ used in agriculture to treat soils that are too acidic in nature. We can also use it if you are a gymnast or rock climber to remove the perspiration in your hand. Did you know even your toothpaste has a small amount of chalk in it used for special dental grade and is much softer than tooth enamel which is good for the tooth.

Dr. Pooja Maheshwari
Assistant Professor
Department of Chemistry
Poddar International College