Chalk and marble are different forms of

Chalk and marble are different forms of

Calcium hydrogen carbonate
Calcium carbonate
Calcium acetate
Sodium carbonate
This question was previously asked in
UPSC NDA-2 – 2020
Chalk and marble are both naturally occurring forms of calcium carbonate (CaCO₃).
– Calcium carbonate is a common substance found in rocks as the minerals calcite and aragonite.
– Marble is a metamorphic rock composed primarily of recrystallized carbonate minerals, most commonly calcite.
– Chalk is a soft, white, porous sedimentary rock, a form of limestone composed primarily of the mineral calcite.
– While chemically the same (CaCO₃), chalk, limestone, and marble differ in their crystal structure, formation process, and physical properties like hardness and texture.
– Calcium carbonate is also the main component of shells of marine organisms, snails, and eggshells.