Diuris basaltica is a tuberous, perennial herb tall with between three and seven linear, green leaves, each long and wide. There are up to three bright golden yellow to orange-yellow flowers, wide with a few dark streaks. The flowers often do not open widely and lean downwards. The dorsal sepal is long, wide and more or less erect. The lateral sepals curve downwards, long, wide. The ear-like petals are egg-shaped, long, wide with a green stalk, long. The labellum has three lobes, the lateral ones small, wedge-shaped and pimply. The middle lobe is broadly egg-shaped, long, wide with two widely separated ridges near the base and a central ridge extending almost to its tip. Flowering occurs from September to October.
