Chloritoid schist - Arran
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Fact sheet
Description: 

This rock was deposited in the late Proterozoic period, probably as a series of silts and muds, before being subject to regional metamorphism in the Grampian orogeny. It now forms part of the Dalradian succession in Scotland within the chloritoid zone; Barrovian metamorphic zone (Barrow zones include chlorite-biotite-garnet-staurolite-kyanite-sillimanite). This samples comes from an area adjacent to The Craw, Catacoul bay, the Isle of Arran, Scotland.

The thin section illustrates the folded metasedimentary banding, with fine grained quartz, muscovite, and chlorite. Large porphyroblasts of chloritoid exhibit greenish brown/blue pleochroism, blocky shapes and poor cleavage. There are also books of chlorite visible at the edges of the chloritoid infilling pressure shadows. Chlorite exhibits green colours and and strong cleavage and between crossed polars it has anomalous blue/brown birefringence colours.

In Place
In Time
infoImage: 
Location description: 
The Craw, Catacol, Isle of Arran, Scotland
Accuracy:
Location precision: 
Good
Timescale:
Timescale: 
Silurian
Ma = Millions of years ago
In Focus
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Type:
Type: 
metamorphic
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