• Formation of Limestone
  

Limestone is the most abundant of the non-clastic sedimentary rocks. Limestone is produced from the mineral calcite (calcium carbonate) and sediment. The main source of limestone is the limy ooze formed in the ocean. The calcium carbonate can be precipitated from ocean water or it can be formed from sea creatures that secrete lime such as algae and coral.

Most sedimentary rocks are formed when weathering crumbles the parent rock to such a small size that they can be carried by wind or water. Those particles suspended in water collide with one another countless times gradually becoming smaller and more rounded. When water is moving quickly due to flooding or due to a rapid change in elevation, larger particles can be carried by the streams and rivers but when the water slows down the particles begin to settle out. The particles dropped from water and wind are called sediment. As layers become thicker, the bottom particles get squeezed closer and closer together under the crushing weight.

Many of the organisms that live in the oceans have shells and skeletons that are made of calcium carbonate. Their decay releases a natural cement into the water. The cement glues the particles of rock back together forming sedimentary rock. People who live in homes with hard water see the amazing affect of this calcium carbonate glue in their showerheads as the holes gradually become closed until the spray is reduced to a trickle.