It is a small orchid with up to eighteen dark, purplish-black flowers and is only known from six sites on the south coast where it grows in shallow soil over rhyolite.

Genoplesium rhyoliticum is a terrestrial, perennial, deciduous, herb with an underground tuber and a single thin leaf 100–150 mm (4–6 in) long and fused to the flowering stem with the free part 10–15 mm (0.4–0.6 in) long.

[2][3][4] Genoplesium rhyoliticum was first described in 1991 by David Jones and Mark Clements from a specimen collected near Pambula and the description was published in Australian orchid Research.

[5] The specific epithet (rhyoliticum) refers to the rock type on which this orchid grows.

[4][6][7] Of the six populations of G. rhyoliticum, three occur in the South East Forests National Park and the only known threat to the species is grazing by native mammals.