MARBLE
Marble is formed from limestone by heat and pressure in the earth's crust. These forces caused the limestone to change in texture and makeup. This process is called recrystallisation.Fossilised minerals in the limestone, along with it's original carbonate minerals, recrystallise and form large, coarse grains of calcite. Impurities present in the limestone during this process affect the mineral composition of the marble that forms. The minerals that result from impurities gives marble a wide variety of colours, while purest calcite marble is white. Most marble of commercial value was formed in the Palaeozoic Era or earlier in Percambrian time.
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