Elvan

Elvan is a name used in Cornwall and Devon for the native varieties of quartz-porphyry.

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.

"White elvans" are a group of fine-grained, acid igneous rocks, while "blue elvans" or "greenstones" are various unusual basic igneous rocks.

Some older descriptions of building stones have called "white elvans" limestone, e.g. in studies of Lemon Street, Truro.

[5] Although the quarry has not been identified, it has been suggested that the Gear (grid reference SW479293), a rock now submerged half a mile from the shore at Penzance, may be the site.