Rockwood or in Afrikaans kliphout (stone wood), as Heeria argentea is commonly known, has rough brown or grey bark with a mottled appearance. Young stems are dull orange-green, turning pale grey or whitish. The stem exudes watery latex when damaged.

The leaves are simple and opposite to spirally arranged. Leaf shape is oblong with a rounded, sometimes notched tip and tapering base. Leaf colour is dark green above. Fine hairs grow on the lower leaf surfaces. The leaf midrib is conspicuous and cream coloured. Lateral veins are notably parallel, continuing to the margins and prominent on the lower surfaces.

Small white or cream flowers grow in sparse, axillary and terminal sprays or panicles. They have five, rounded cream coloured corolla lobes. Male and female flowers usually appear on separate trees. Blooming time is from midsummer to midwinter.

The fruit starts off reddish, turning pale green and finally shiny black with a rough surface. The drupe is oblong in shape (Coates Palgrave, 2002; Van Wyk and Van Wyk, 1997).