There are different combinations of colours and patterns in the pebbles of different beaches in the Channel Island of Guernsey. The assortment of pebbles in each location reflects the local geology of that area. There is a higher proportion of metamorphosed rocks compared with igneous rocks on the southern coast of the island, as seen here for Havelet which is just west of St Peter Port. Many of the rocks belong to the Southern Metamorphic Region dating back as far as 2,500 million years ago. Rocks from this region include gneisses and schists. The pebbles at Havelet can be compared with accumulations of pebbles on the north coast, such as those at Albecq, where the stones are mostly derived from younger igneous rocks such as granite, diorite and gabbro dating from about 700 million years ago in what is known as the Northern Igneous Complex.
British Geological Survey Classical areas of British geology: Guernsey, Channel Islands Sheet, 1 (Solid and Drift) Scale 1:25,000. NERC, Crown Copyright 1986.
De Pomerai, M. and Robinson A. 1994 The Rocks and Scenery of Guernsey, illustrated by Nicola Tomlins, Guernsey: La Société Guernesiaise, ISBN 0 9518075 2 8.
Roach, R. A., Topley, C. G., Brown, M., Bland, A. M. and D’Lemos, R. S. 1991. Outline and Guide to the Geology of Guernsey, Itinerary 9 – Jerbourg Peninsula, pp 21 – 22, & 75 – 78. Guernsey Museum Monograph No. 3, Gloucestershire: Alan Sutton Publishing. ISBN 1 871560 02 0.