Monday, May 2, 2011

Chalk (pronunciation: /ˈtʃɔːk/) is a soft, white, porous sedimentary carbonate rock, a form of limestone composed of the mineral calcite.




Chalk (pronunciation: /ˈtʃɔːk/) is a soft, white, porous sedimentary carbonate rock, a form of limestone composed of the mineral calcite. 











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