The Granite and Greisen of Cligga Head (Western Cornwall)

Abstract

The small mass of granite known as Cligga Head, forming a bold promontory between St. Agnes and Perranporth on the northern coast of Western Cornwall, has long been known, not only to the geologists of that county, but also to others from farther afield. Conybeare, in 1817, from notes by Buckland, described a small formation at Cligga Point which would ‘probably be considered by the Wernerian school as the newer granite,’ and remarked on tho stratification and the fact that it was worked for tin. A sketch also is given of the headland ( op. cit. pl. xxiii), which does not, however, show the leading features exactly as they occur. In 1818, Joseph Carne spoke of granite at Cligga Head, apparently stratified obliquely, but proving, on a nearer view, to be traversed by small veins of ‘blackish quartz, whose contemporaneous formation can scarcely be doubted.’ In a footnote the same author wrote:— ‘The granite at Cligga Point (if it is not a large elvan-coarse) might be called secondary or transition granite, without affecting the age of the granite of other parts of Cornwall, as it is far from the large granite-chain’ ( op. cit. pp. 74–75). In 1820 Sedgwick gave a description of the granite, as resembling the common granite of the country, except the ‘intermediate parts,’ which exhibited varied modes of aggregation: the strong folding of the parallel ‘beds’ in the granite was also noticed. Œynhausen & Dechen, in 1829, noted the ‘numberless veins of granite which interest the granite itself,’