Types of natural stone
Limestone is a sedimentary rock composed mainly of calcium carbonate (CaCO3).
Limestone has two origins:
1. Biogenic precipitation from seawater, the primary agents being lime-secreting organisms and foraminifera;
2. Bechanical transport and deposition of pre-existing limestones, forming clastic deposits. Travertine, tufa, caliche, chalk, sparite, and micrite are all varieties of limestone.