Buff coloured rock.
Almost pure quartz, which has been very well recrystallised.
Faint banding could be original bedding.
Fine to medium grained recrystallised quartz with sutured contacts.
The sutured (ragged) grain boundaries and undulose extinction of the quartz grains indicate that this rock formed under relatively low temperature metamorphism. Had the rock been raised to higher temperatures perfect 120° grain boundaries would have formed, and the quartz would not be strained.
Inserting the sensitive tint plate results in the vast majority of grains changing colour in the same way – most of the grains simultaneously display higher interference colours in one orientation, and lower interference colours in the other orientation. This strong fabric was produced by recrystallisation under directed stress, which caused all the grains to elongate in one direction.
Precambrian
Braemar, Aberdeenshire
Buff coloured rock.
Almost pure quartz, which has been very well recrystallised.
Faint banding could be original bedding.
Fine to medium grained recrystallised quartz with sutured contacts.
The sutured (ragged) grain boundaries and undulose extinction of the quartz grains indicate that this rock formed under relatively low temperature metamorphism. Had the rock been raised to higher temperatures perfect 120° grain boundaries would have formed, and the quartz would not be strained.
Inserting the sensitive tint plate results in the vast majority of grains changing colour in the same way – most of the grains simultaneously display higher interference colours in one orientation, and lower interference colours in the other orientation. This strong fabric was produced by recrystallisation under directed stress, which caused all the grains to elongate in one direction.