Tourmaline Aplite - Rostowrack (#40)
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Fact sheet
Description: 

This sample provides a good illustration of trapped volatiles in a granitic magma. At the very end of the magmatic cycle boron-rich volatiles become concentrated and here they have been preserved in the form of tourmaline "balls" - each representing a bubble of volatiles. The rock is an aplite that intruded earlier granite (from the first phase of igneous activity in this region).

In thin section note the fine grain size of the matrix, the considerable alteration of feldspar and the pools of tourmaline mantled by quartz.

In Place
In Time
Location description: 
Restowrack SW china clay pit, near St Dennis, Cornwall
Accuracy:
Location precision: 
Moderate
Timescale:
Timescale: 
Permian
Ma = Millions of years ago
In Focus
Collection:
What\
Type:
Type: 
igneous
What\
Rock-forming minerals:

Rock forming mineral:

What\