Limestone is defined as a rock of sedimentary origin composed mainly of calcium carbonate or the double carbonate of calcium and magnesium, or a combination of both minerals.
Re-crystallized limestones, compact microcrystalline limestones, and travertine that are capable of taking a polish are promoted, marketed and sold as either limestone or marble, mainly in the United States.
Limestone is divided into three (sub-classifications) based on their densities as listed below:
Low Density: Limestone with a density ranging from 110 to 135 lb/ft3 (1760 through 2160 Kg/M3).
Medium Density: Limestone having a density greater than 135 but not greater than 160 lb/ft3 (2160 to 2560 Kg/M3).
‘High Density: Limestone having a density greater than 160 lb/ft3 (2560 Kg/M3).
Limestone contains a number of distinguishable natural characteristics, including calcite spots or streaks, fossils or shell formations, pit holes, reedy formations, open texture streaks, honeycomb formations, iron spots, travertine-like formations and grain formation changes. One or a combination of these characteristics will affect the texture.