Portland Stone
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Fact sheet
Description: 

This oolitic limestone rock was deposited in a warm shallow sea not far from land during the Jurassic period around 140 million years ago. The sample comes from a quarry on the Isle of Portland, hence the name Portland stone. Portland stone has been used as a building stone since Roman times and was used in the construction of Buckingham Palace and St Paul's Cathedral.

The thin section shows that the rock is dominated by spherical ooids with cores of shell fragments and quartz, sand-coated by carbonate micrite cement in concentric layers. The rock also contains shell fragments, including fragments of bivalves, ammonites and corals. Some of the pore spaces between shell fragments and ooids remain open but the majority are cemented by micrite and sparry calcite. The almost complete filling of pore spaces in this limestone by cemented micrite and sparry calcite has made it more resistant to erosion and thus a good building stone.

In Place
In Time
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Location description: 
Weston quarries, Portland, Dorset
Accuracy:
Location precision: 
Moderate
Timescale:
Timescale: 
Jurassic
Ma = Millions of years ago
In Focus
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Type:
Type: 
sedimentary
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