Bluestones are bluish volcanic rocks of spotted dolerite found in West Wales.
A precipitous dolerite crag forms the perfect defence on the two seaward sides of the castle.
The peaks are resistant "spires" of Jurassic dolerite, lying over older rocks of Triassic-Permian sediments.
Dr Gibb is a specialist in igneous rocks who has done mould-breaking research into the beautiful columnar dolerites of the Hebrides.
These observations can be explained by the fact that felsic granulite requires more fluid infiltration to equilibrate than mafic granulite and dolerite.
Subangular to subrounded fragments of basalt and dolerite of boulder to granule sizes are contained in a red granule matrix.
Thin-section analysis of one rock sample identified it as a dolerite.
