Arising mainly from its exceptionally varied suites of intrusive igneous rocks, Cornwall has a rich variety of building and decorative stones which were extensively exploited, both for local and export use, before concrete and brick came to dominate construction in the 20th century. Basic igneous rocks include a metabasic rock at Cataclews Point, west of Padstow, which provided the extremely durable Cataclews Stone from Norman times onwards; this was used extensively for medieval fonts and church carvings in North Cornwall. Polyphant Stone, formed by carbonatization of an ultrabas intrusion, is composed of a mixture of talc, chlorite and various calcium and magnesium carbonates and the Polyphant quarry was recently reopened to supply stone for the rebuilding of Newquay parish church. Allied to Polyphant Stone is Duporth Stone, worked from the cliffs of Duporth Bay, south of St. Austell and used extensively in the pillars of Truro Cathedral. Granites were notably worked in the eastern part of the Carnmenellis Granite (mainly in Mabe parish), in the St. Austell Granite (Luxulyan, Carn Grey and the china stone areas) and on Bodmin Moor (De Lank, Hantergantick, Cheesewring, etc). A significant industry developed in the 19th and early 20th centuries, employing large numbers of skilled quarrymen, with granite exported world-wide. A tourmalinized granite, luxullianite, was an important decorative stone, used for example in the Duke of Wellington's sarcophagus in St. Paul's cathedral. Allied to the granites are the fine-grained elvans of granitic composition, usually emplaced as dykes. These have yielded durable freestones used in the construction of buildings such as St.Austell church tower, Place (Fowey) and the Georgian buildings of Lemon Street in Truro. The best known elvan quarries were at Pentewan, but not all buildings described by architectural historians as being of Pentewan Stone came from Pentewan, Another important elvan building stone was Newham Stone, widely used in the older buildings in Truro. Tremore elvan was also used, together with luxullianite, as a decorative stone, to line Porphyry Hall at Place in Fowey. Sedimentary and metasedimentary rocks have also been used as building materials in Cornwall. States and sandstones of Devonian and Carboniferous age are extensively used for traditional buildings throughout Cornwall, and are widely used in the construction of Cornish hedges alongside road developments. The geologically youngest building stone, seen in the Newquay and Padstow areas, is a cemented bioclastic beach sand (locally known as "sandrock") and used, for example, in the construction of St. Carantoc's church,it Crantock. In terms of maintaining Cornwall's heritage, there is a long overdue need to identify and conserve the sources of Cornish building and decorative stones, such as those mentioned above, which give the local built environment so much of its character.
