Quartz-Tourmaline Rock - Roche (#209)
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Fact sheet
Description: 

This sample is an excellent example of a prominent outcrop of quartz ‘schorl’ rock from Roche, close to the town of St Austell. The outcrop is part of the northern flank of the St Austell granite. Schorl is the species name for sodium-iron tourmaline commonly found in certain types of granitic rock. It may represent the roof of the magma chamber. The outcrop consists of numerous interleaved pegmatite sheets and many cavities filled with quartz, tourmaline, zinnwaldite and topaz.

The thin section consists of just two minerals; elongate and stubby tourmaline grains exhibiting blue/pale brown pleochroism and second order birefringence colours; and large plates of underformed quartz, exhibiting first order birefringence colours and high concentrations of solid and fluid inclusions that make them appear dusty.

In Place
In Time
Location description: 
Roche Rock, Roche, near St Austell, Cornwall
Accuracy:
Timescale:
Timescale: 
Permian
Ma = Millions of years ago
In Focus
Collection:
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Type:
Type: 
igneous
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Rock-forming minerals:

Rock forming mineral:

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