Limestone, Size : 4x4 Ft

Limestone is calcareous sedimentary rocks formed at the bottom of lakes and seas with the accumulation of shells, bones and other calcium rich goods. It is composed of calcite (CaCO3). The organic matter upon which it settles in lakes or seas, are preserved as fossils. Over thousands and millions of years, layer after layer is built up adding weight. The heat and pressure causes chemical reaction at the bottom and the sediments turn into solid stone, the limestone.
The rock which contain more than 95% of calcium carbonate is known as high-calcium limestone. Recrystallised limestone takes good polish and is usually used as decorative and building stone.
A part of calcium molecules if being replaced by magnesium, it is known as magnesium lime stone or dolomite limestone.
Limestone that will take a polish are considered marbles by most people, but technically, if there are still shells visible or the structure is not crystalline, it is still a limestone.
Physical Properties of Limestone
Physically, Limestones are Quite impervious, Hard, Compact, fine to very fine grained calcareous rocks of sedimentary nature.