Limestone is a sedimentary rock composed largely of the mineral calcite (calcium carbonate: CaC03). The primary source of the calcite in limestone is most commonly marine organisms. These organisms secreted shells (300 million years ago) that settled out of the water columns and were deposited on the ancient ocean floors. Another form taken by calcite is that of oolitis (oolitic limestone) which can be recognized by its granular appearance. Limestone makes up about 10% of the total volume of all sedimentary rocks.
Limestone is very common in architecture, especially in North America and Europe. Many landmarks across the world, including the Great Pyramid and its associated complex in Giza Egypt, are made of limestone. Limestone is readily available and relatively easy to cut into blocks or to shape into architectural features and is a very popular material with stone carvers. Limestone was a popular building block in the middle ages, as it was readily available, hard and durable. Many medieval churches and castles in Europe are made of limestone. Limestone reached its current popularity starting in the 19th century and extending on into the 21st century. In the 19th century, it was a popular building material in many banks, train stations and other structures. Expanding into the 20th century with the use as a façade on skyscrapers and in many of national monuments. Today, the uses of limestone are almost unlimited. Architectural features on custom homes, panels and architectural features on large commercial buildings, large and small custom carved pieces, flooring both interior and exterior, fireplace surrounds, columns of all types, balustrade, pier caps, finials, pool coping and decking, chimneys and chimney caps, benches and tables, fountains, niches, water table, banding and signage are examples of limestone’s versatility.