Portland stone
**Geology and Formation**:
– Portland stone formed in a marine environment in a shallow, warm, sub-tropical sea.
– Seawater releases dissolved carbon dioxide as a gas, forming calcium carbonate.
– Lime mud accumulated on the sea floor, with particles forming calcite layers.
– Oolitic limestone formed from billions of calcite balls partially cemented together.
– Portland stone measures 3.5 on the Mohs scale of mineral hardness.
**History and Use**:
– Stone quarrying on Portland dates back to Roman times.
– Extraction as an industry began in the early 17th century.
– Portland stone was used for St. Paul’s Cathedral in London.
– Companies like Albion Stone PLC and Portland Stone Firms Ltd have been quarrying the stone since the 1980s and 1990s.
– Famous buildings like Palace of Westminster and Tower of London built with Portland stone.
**Quarries, Mines, and Quarrying Methods**:
– Jordans Mine is the biggest mine on Portland, using mining techniques.
– Bowers Quarry has been operational since the late 18th century.
– Stonehills Mine is a new mine estimated to last for 50 years.
– Traditional quarrying methods involved gunpowder and plugs and feathers.
– Modern methods involve diamond bladed cutting machines and wire saws.
**Restoration, Preservation, and Memorials**:
– Once quarries are worked, they are restored to their original state.
– The Portland Sculpture and Quarry Trust is dedicated to preserving stone knowledge.
– Memorials like the Cenotaph in Whitehall and RAF Bomber Command Memorial use Portland stone.
– The trust holds workshops at Tout Quarry annually.
– Tout Quarry, donated by Portland Stone Firms, is a non-working quarry.
**Applications, Technology, and Substitution**:
– Portland stone used in various structures worldwide.
– Italian stone cutting equipment introduced in 1999 improved quarrying methods.
– Portland stone designated as a Global Heritage Stone Resource.
– Substitution controversies with Anstrude Roche Claire stone from France.
– ‘Portland cement’ coined by Joseph Aspdin in 1824, resembling Roman cement.https://en.wikipedia.org/wiki/Portland_stone