The fruiting body is somewhat tongue-shaped, with no discernable stalk, and the tough flesh is 1–3 millimetres (1⁄16–1⁄8 in) thick. The cap is flat, up to 10 centimetres (4 in) across.[5] It is often triangular or round, with zones of fine hairs coloured rust-brown or darker brown, sometimes with black zones.[5] Underneath a layer of tomentum is a black layer, topping the whitish flesh.[6] Older specimens can have zones with green algae growing on them.[5]
The bottom surface of the cap shows typical concentric zones of different colors, with the margin always the lightest.[7] There are 3–5 pores per mm. They are whitish to light brown,[5] with pores round and with age twisted and labyrinthine.