Portland stone is a limestone geological formation dating to the Tithonian age of the Late Jurassic that is quarried on the Isle of Portland in Dorset, England. The quarries are cut in beds of white-grey limestone separated by chert beds. It has been used extensively as a building stone throughout the British Isles, notably in major public buildings in London such as St Paul's Cathedral and Buckingham Palace. Portland stone is also exported to many countries, being used for example at the United Nations headquarters in New York City.
Portland stone quarry on the Isle of Portland
The Cenotaph, in Whitehall, London, is made from Portland stone
The tramway incline from the Admiralty Quarry seen from Castletown, Portland
Portland stone quarry on the Isle of Portland, Dorset.
Limestone is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of CaCO3. Limestone forms when these minerals precipitate out of water containing dissolved calcium. This can take place through both biological and nonbiological processes, though biological processes, such as the accumulation of corals and shells in the sea, have likely been more important for the last 540 million years. Limestone often contains fossils which provide scientists with information on ancient environments and on the evolution of life.
Limestone outcrop in the Torcal de Antequera nature reserve of Málaga, Spain
This limestone deposit in the karst of Dinaric Alps near Sinj, Croatia, was formed in the Eocene.
Ooids from a beach on Joulter's Cay, The Bahamas
Ooids in limestone of the Carmel Formation (Middle Jurassic) of southwestern Utah.