Marble is formed from limestone when the limestone is affected by heat and high pressure during a process known as metamorphism. During metamorphism the calcite limestone recrystallizes, forming the interlocking calcite crystals that make up the marble.
Metamorphism occurs in limestone when the limestone is located to convergent plate boundaries or when it is heated by a nearby body of hot magma. Prior to the conversion to marble, the calcite in the limestone consists primarily of mineralized fossil material, along with some biological material. When the heat and pressure hits the limestone, calcite seed crystals form. With continued metamorphism, these crystal seeds, grow while any clay deposits in the limestone transform into silicate structures such as mica.
Because marble is a fairly soft material, only a three on the Mohs hardness scale, it is easy to cut and carve. This makes marble a useful material for creating sculptures with, along with decorative flooring, or wall materials. When sanded, it gains a lustrous finish with a slightly translucent quality. Marble is also used as a calcium additive in animal feed for increased production from egg-producing chickens and dairy cows, as well as for a cleaning abrasive once finely ground. Ground marble also neutralizes acids and is particularly used for industrial and large-scale environmental applications.