Elvan is a name used in

Cornwall Cornwall (; kw, Kernow ) is a Historic counties of England, historic county and Ceremonial counties of England, ceremonial county in South West England. It is recognised as one of the Celtic nations, and is the homeland of the Cornish people ...

and

Devon Devon ( , historically known as Devonshire , ) is a ceremonial and non-metropolitan county in South West England. The most populous settlement in Devon is the city of Plymouth, followed by Devon's county town, the city of Exeter. Devo ...

for the native varieties of

quartz-porphyry Quartz-porphyry, in layman's terms, is a type of volcanic (igneous) rock containing large porphyritic crystals of quartz. These rocks are classified as ''hemi-crystalline acid rocks''. Structure The quartz crystals exist in a fine-grained matrix ...

. They are dispersed irregularly in the

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, wh ...

series of rocks and some of them make very fine building stones (e.g. Pentewan stone, Polyphant stone and Catacleuse stone). Greenstone is another name for this stone and it is often used for parts of buildings such as doorways so they can be finely carved. Most of the elvan quarries are now disused. Others are quarried in bulk for aggregates commonly used for road-building. More precisely there are two types of rock in this category: one is "white elvan" and the other is "blue elvan". "White elvans" are a group of fine-grained, acid igneous rocks, while "blue elvans" or "greenstones" are various unusual basic igneous rocks. "White elvan" comes from various different locations and is often known as Pentewan stone (or by other names based on the location). Some older descriptions of building stones have called "white elvans" limestone, e.g. in studies of Lemon Street, Truro.

Archaeology

Approximately 400 prehistoric stone axes, known as Group 1 axes and made from greenstone, have been found all over Britain, which from petrological analysis appear to come from west Cornwall.Markham, M. & Floyd, P. A. (1998) "Geochemical Fingerprinting of West Cornish Greenstones as an aid to Provenancing Neolithic Axes". Read at the Annual Conference of the Ussher Society, January 1998 Although the quarry has not been identified, it has been suggested that the ''Gear'' (), a rock now submerged half a mile from the shore at

Penzance Penzance ( ; kw, Pennsans) is a town, civil parish and port in the Penwith district of Cornwall, United Kingdom. It is the most westerly major town in Cornwall and is about west-southwest of Plymouth and west-southwest of London. Situ ...

, may be the site. A significant amount of trade is indicated as many have been found elsewhere in Britain.Pool, P. A. S. (1974) ''The History of the Town and Borough of Penzance.'' Penzance: The Corporation of Penzance. Neolithic greenstone axe roughout (plan) (FindID 258401)

Neolithic greenstone axe roughout (plan) (FindID 258401)

Archaeology

References

Further reading