Biotite granite - Luxulyan
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Fact sheet
Description: 

This sample of biotite-rich granite comes from the Luxulyan quarry in the Luxulyan Valley in south east Cornwall. This sample is a less evolved portion of the intrusion, which was associated with the tourmaline and topaz-rich intrusions and mineralisation. The valley is part of a World Heritage Site containing the remains of extensive early 19th century industrial activity, including mining and quarrying, which at its peak included several water wheels and steam engines.

The thin section illustrates the quartz-rich nature of the rock, which also contains altered orthoclase, plagioclase and both biotite and muscovite. The biotite is notably rich in pleochroic haloes, indicating a high proportion of zircon and monazite crystals.

In Place
In Time
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Location description: 
Luxulyan quarry, Luxulyan, near St Austell, Cornwall
Accuracy:
Location precision: 
Good
Timescale:
Timescale: 
Permian
Ma = Millions of years ago
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Type: 
igneous
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