This picture shows unweather granite from east Dartmoor. The black specks are biotite mica, some of it glinting in the light, there is a large whiteish feldspar (which has been split by the quarring process), a ground mass of fairly clear quartz and feldspar, and towards the upper left a diffuse black patch where tourmaline has replaced some of the groundmass.

Granite close up

Part of a small vein. A series of veins cross our farm on a west to east trend. Mineralisation is, as far as I can find, exclusively quartz haematite and tourmaline with accesory chlorite.

Quartz/haematite vein