The rocks consist chiefly of basalt, dolerite, melaphyre and felstone.
The minerals of diabase are the same as those of dolerite, viz.
The boundary between these formations is also marked by the development of masses of dolerite and clayey basalt.
The dolerite of Fair Head sends off sheets along the bedding-planes of these carboniferous strata.
Generally speaking, the soils produced from diorite are superior to those from dolerite.
The terms diabase and dolerite are employed really to designate distinct facies of the same set of rocks.
As the rocks lie in a horizontal position, on most of the islands of the group only the basalts or dolerite are visible.
dolerite was brought from Arabia, cedar from Syria, gold and precious stones from the east.
Still later, dolerite sills and sheets and dikes of granophyre and quartz felsite followed in the same region.
It is traversed in places by dikes and sills of diabase or dolerite, while bosses of more or less altered gabbro rise through it.