A British meta‐anthracitic coal of Devonian age

Abstract Vitrinite from the Devonian Gramscatho Beds at Pendower in southwestern Cornwall displays optical properties which indicate an extremely high rank (meta‐anthracite). Despite this high rank, wood structures are clearly evident in polished sections between crossed polars. Some coke is present and this feature, together with the optical properties of the main vitrinite mass, suggests that relatively high temperatures (probably in excess of 350°C), were associated with the metamorphism of the host rocks. Reflectivity measurements on oriented blocks show that the vitrinite is optically biaxial, which conflicts with the widely accepted view that vitrinites are negative uniaxial materials.