Crystals are found as a rarity in the amygdaloidal cavities of igneous rocks.
It occurs in a series of amygdaloidal dolerites or diabases, and in the associated sandstones and conglomerates.
These plateaus are composed of nearly horizontal sheets of basalt - columnar, amorphous or amygdaloidal - which, in Ben More, in Mull, attain a thickness of more than 3000 ft.
Near Haco's Ness in Shapinsay there is a small exposure of amygdaloidal diabase which is of course older than that in Hoy.
This consists largely of rocks of igneous origin, of which the amygdaloidal diabase of Klipriversberg forms the type.
The copper of the Lake Superior region is in the Keweenawaii system, chiefly in its sedimentary and amygdaloidal parts.
Of boulder beds and amygdaloidal lavas belonging to the Vaal River System.
The Old Man presents a characteristic section, for it exhibits a thick pile of massive, current-bedded red sandstones, resting, near the foot of the pinnacle, upon a thin bed of amygdaloidal porphyrite, which in its turn lies unconformably upon steeply inclined flagstones.