Area: 0.47 hectares.
Description and Reasons for Notification:
This is a new Geological Conservation Review site.
Cameron Quarry, situated at the south-western end of the St Agnes/Cligga Head granite ridge, provides the only surface exposure of the contact of the St Agnes Granite cusp. The quarry provides an excellent demonstration of a sequence of greisenisation, silicification and mineralisation as a result of late-stage magmatic activity.
The only surface exposure of the contact of the Carboniferous-Permian St Agnes cupola is seen in the northern part of this quarry. The granite is pervasively greisened and the effects of alteration extend into the country rocks. However, in contrast to Cligga Head, the greisening is not joint controlled but has permeated throughout the granite, probably because high fluid pressure had shattered the already consolidated granite and created microfractures which made such pervasive alteration possible. Complex mineralisation, including tin and tungsten, is also present and for the most part can be shown to follow later post-greisen fractures.
This site is of national importance as the only site in Britain showing pervasive greisening of granite.