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Limestone
3-10 usd/kg
Limestone is a sedimentary rock composed mainly of calcium carbonate (CaCO3). It is formed underwater water and so often contains fossils of coral and shells, and other organisms that contributed to its formation. Its grain structure is often formed of the fragments of fossilised animal shells.
Quarried limestone has many uses beyond building stone, including providing the feedstock for lime used in cement and hempcrete, glass making, agriculture (fertiliser) and as a pigment. There are several other varieties, too. Travertine, a type of terrestrial limestone, is formed from deposits around rivers and mineral springs (stalactites and stalagmites, for example). Coquina is a type of soft limestone formed almost exclusively from fossilised shells cemented together.
Sustainability concerns
Non-renewable ingredients
Raw material generates polluting by-products
Low circularity potential
Limestone is typically white through grey. Other colours, such as off-white to yellow, are the result of the inclusion of trace amounts of iron or manganese. Limestone used in buildings, interiors, furniture and monuments is dense (there are many varieties of limestone and some are denser than other – both chalk and marble are based on limestone), with high compressive strength, far superior to normal concrete (10-50 MPa). It has been used in architecture and construction throughout history, including cladding the Great Pyramid of Giza, railway stations and other grand public buildings.
Like marble, limestone is relatively soft, porous and vulnerable to staining, wear and abrasion. Therefore, it tends to be used as wall cladding and in furniture, where it will not be exposed to heavy traffic. It is dissolved by acids and so vulnerable to certain types of food and cleaning products.
Weathering can also have a degrading effect on limestone, especially acidic rainwater. The most common effect is the loss of fine details. It is also stained by run-off from metals, such as iron and copper.
