When Is Marble Formed?
Marble is formed when granular limestone or dolomite rocks crystallize twice under the influence of heat, pressure, liquids and chemical action. These rocks undergo what is known as metamorphism, a complete change from one state to another. Marble forms under such conditions because the calcite forming the limestone recrystallises forming a denser rock consisting of roughly equigranular calcite crystals.
The variety of colours exhibited by marble are a consequence of minor amounts of impurities being incorporated with the calcite during metamorphism. While marble can appear superficially similar to quartzite, a piece of marble will be able to be scratched by a metal blade, and marble will fizz on contact with dilute hydrochloric acid.
Most of the marble existing today was formed many millions of years ago and is usually quarried from deep under the earth. It is used for buildings and monuments, sculpture and table tops. The chief discoveries of marble have been made in Italy (Carrara marble), Mexico, the United States (onyx), Norway and Greece.
The famous marbles from Carrara would have a geological age of 200 million years. The Makrana marble in Rajastan is supposedly 150 million years old, the Crema Marfil from Spain was formed, 75 million years, and the Egyptian limestones’ only’ 60 million years. That is what makes natural stone a unique product!