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Last edited 14 Jan 2021
|St Paul’s Cathedral.|
Limestone is a sedimentary rock formed during four geological eras: Cretaceous, Jurassic, Permian and Carboniferous, 70 – 345 million years ago. It consists of calcium carbonate, and is formed by the compaction of calcite, primarily from marine organisms, at the bottom of shallow lakes and seas. The presence of marine organisms and other fossil inclusion is often noticeable in limestone. Due to the presence of a variety of minerals, limestone also presents numerous colours, ranging from light grey Portland Stone, to creamy Bath stone and dark grey Purbeck stone.
Portland Stone was formed at the end of the Jurassic period, approximately 145 million years ago. It has been quarried on the Isle of Portland in Dorset since Roman times, and has been used as a building material in London since the 14th century, when it was used in the construction of the Palace of Westminster, the Tower of London and London Bridge. St Paul’s Cathedral, designed by Sir Christopher Wren, was built from Portland Stone, establishing it as the stone of choice for London. During the 19th and early 20th centuries Portland Stone, became popular for building banks, civic buildings and educational establishments, many of which were in the classical style.
It is strong, durable, resistant to weathering, easy to work and carve and can be used for masonry walls, cladding, columns, plinths, flooring, paving, mouldings, sculptures, fireplaces and so on. There are a number of different varieties of Portland Stone, with different appearances, properties and recommended uses depending on the bed that it has been extracted from. These include:
- Bowers Basebed.
- Bowers Roach.
- Fancy Beach Whitbed.
- Grove Whitbed.
- Jordans Basebed.
- Jordans Whitbed.
- Ostrea Patch Reef Whitbed.
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