What Exactly is Limestone?
Limestone is a sedimentary rock made up primarily of calcium carbonate which is a chemial compound that occurs in rocks as the minerals calcite and aragonite.
Large quantities of limestone are formed from the skeletal remains of marine organisms left behind after they die. It ususally forms in clear, calm, warm and shallow bodies of water.
Limestone is very soft so scratches easily. Its colour is usually an even white to off-white, the stone doesn't take on a high a polish so the lustre is normally dull.
Chalk is one of several types of limestone, another is travertine.
Limestone also forms slowly over millions of years from the evaporation of water in caves. Stalactites and stalagmites are examples of limestone that formed in this way.