Looking west is the granite contact with the engine houses of Trewavas Mine, which mined copper lodes in the granite. On the foreshore at Megiliggar can be seen examples of pegmatite and aplite extending out from the granite as flat sheets or sills into country rocks of mudstones (pelites). The exposure illustrates the invasion of the granite into country rocks by stoping and the formation of comb layer pegmatites and aplites. These were formed as stoped blocks fall and there is a corresponding pressure change leading to the 'freezing' of the intrusive magma. As well as sill like sheets there are examples of bridging veins. When closely examined the pegmatite contains ore minerals of lollingite and traces of native bismuth, molybdenite, wolframite, cassiterite, and gangue minerals of apatite and fluorite, indicating a build up of volatile magmatic elements. In the cliff section there are examples of crosscourses showing an infilling of quartz and hematite, often these have caused a displacement by faulting.

Bridging vein

The cove illustrates a roof pendant of country rocks surrounded by granite. Just inland there are the ruins of Wheal Prosper, which produced copper and tin from a fissure lode(s). On the foreshore the sharp granite contact can be clearly seen with the country rocks, which have been metamorphosed to hornfels (fine grained metamorphic rock) with metamorphic minerals of andalusite and corderite formed by thermal metamorphism. On the western side of the shore platform are xenoliths of country rock in the granite. One has clearly developed pegmatite on the lower contact and others have been almost completely absorbed. On the eastern side of the cove the granite contact is almost vertical. Quartz veins cross-cut the hornfels and either pre and postdate the granite. In the cliff section, folding is exposed which predated the granite, with an infill of early quartz ('sweat' quartz) from metamorphic fluids.

Quartz veins

On the western side of the beach a 17 m wide rhyolite dyke (known locally as elvan) has been emplaced into the country rocks of pelites (mudstones). The dyke has a strike of NW-SE and follows that of metalliferous fissure lodes in this area. These dykes have been intruded as a later phase of magmatism and are dated at the same age as the fissure lode mineralization. The dyke would appear to have been emplaced in two phases. The first now forms the outer part, which is fine grained and is flow banded. A later inner phase is strongly porphyritic (larger crystals set in a fine grained ground mass).