Contact metamorphosed sandstone
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Fact sheet
Description: 

This unusual rock is a thermally metamorphosed and partially melted Torridonian arkosic sandstone. It came from the foot of Allt Bealac Mhic Neil. The sandstone was subjected to intense contact metamorphism in the margin of a small gabbroioc plug on north side of the Rum Central Complex.

In thin section the rock is dominated by quartz and fine grained feldspar. The most notable feature is the abundant needle-like quartz paramorphs after original tridymite, in other words crystals that were once the high temperature form of silica tridymite that later inverted to quartz. The presence of tridymite would indicate that the metamorphism occurred at low pressure. Note that the paramorphs are commonly fringeing relic quartz grains from the sandstone.

In Place
In Time
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Accuracy:
Location precision: 
Good
Timescale:
Timescale: 
Paleogene
Ma = Millions of years ago
In Focus
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Type:
Type: 
metamorphic
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