Dikes of aplite and pegmatite commonly intrude on Sentinel Granodiorite. V aplite&colon; Metagranite, aplite dikes and layers. There are pegmatite and aplite bodies and veins. The dykes included a swarm of dolerite dykes, also lamprophyre, feldspar porphyry and aplite. Intrusions vary widely, from mountain-range-sized batholiths to thin veinlike fracture fillings of aplite or pegmatite. The aplite minerals include tourmaline, topaz and fluorite. They range from porphyritic alkaline rhyolite to alkaline aplite to porphyritic alkaline granite. The aplite dykes are one to two metres wide. Precambrian basement rock intrusions in the south include aplite, diorite, gabbro and granodiorite. Aplite dikes are fine-grained or sugary-textured intrusives of granitic composition.