Portland stone

Portland Stone Formation
Stratigraphic range: Tithonian PreꞒ Ꞓ O S D C P T J K Pg N ↓
Portland stone quarry on the Isle of Portland
Type	Geological formation
Unit of	Portland Group
Sub-units	Dorset: Portland Chert Member, Portland Freestone Member Vale of Wardour: Tisbury Member, Wockley Member, Chilmark Member Vale of Pewsey: No formal subdivision
Underlies	Lulworth Formation
Overlies	Portland Sand Formation
Thickness	up to 38 metres (120 ft) in Dorset
Lithology
Primary	Limestone
Other	Siltstone, Sandstone
Location
Region	England
Country	United Kingdom
Type section
Named for	Isle of Portland
Location	Clay Ope, West Weare Cliff
Thickness at type section	25 metres

Portland stone is a limestone geological formation (formally named the Portland Stone Formation^[1]) dating to the Tithonian age of the Late Jurassic that is quarried on the Isle of Portland in Dorset, England.^[1] 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.