Typically, the body is almost entirely black, including the wings, except for the fore and mid legs, of which the tibiae and tarsi are yellowish-brown.

Specimens from the southern extent of the species' range may have parts of the head and thorax more or less ferruginous.

[4][5] This species is very similar in appearance to Conocalma brullei but can be distinguished by the lack of an elevated structure on the petiole of the abdomen and by the shape of the clypeus.

Henry and Marjorie Townes later re-evaluated the genus in 1951 and considered the two to represent a single species with two differently-colored subspecies.

[2] G. obsidianator is found across eastern North America from Quebec south to Florida and as far west as Manitoba and New Mexico.