[2] Gymnocalycium robustum grows as a solitary cactus with gray, gray-green, or slightly mauve-colored, flattened spherical stems.

The plant has 9 to 11 broad, flat, blunt ribs that are distinctly cross-grooved and divided into low, chin-like protrusions.

There are 5 to 7 stiff radial spines up to 1.5 cm long, one pointing downward and the others sideways.

When dry, the spines are chalk-white; when moist, they are yellowish with brown tips and bases.

[3] Gymnocalycium robustum is native to southern Santiago del Estero and Córdoba Province of Argentina, growing on granite rocks at elevations of 300 to 600 meters.