The grand skink grows to a similar length as the Otago skink, up to about 300mm. It is coloured black with heavy gold flecking in the form of short dash-like markings. It has a long tapering tail, much longer than its body's SVL. It also has particularly long toes. 

It inhabits the schist rock tors of inland Otago, where it sun basks on the ledges and finds retreat in the deep cracks and fissures of the rock. In particular it likes the rock tors surrounded by tussock grassland and native scrub. The grand skink forages during the day and eats invertebrates, smaller lizards, flowers and soft fruit like berries. It’s an important seed distributor for low growing shrubs such as creeping pōhuehue (Muehlenbeckia axillaris) and snowberry (Gaultheria antipoda). 

The grand skink takes 3 - 5 years to reach sexual maturity, and gives birth to 2 - 4 young once every summer. Often the young sunbask touching or even on top of the mother. It can live for about 30 years. 

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There are two distinct populations of grand skinks, the western and the eastern. These two populations are separate enough to show genetic differences. They are also able to be distinguished by eye, the western variety being slightly smaller with thin gold stripes and a less patterned tail, while the eastern variety has shorter gold streaks and a boldly patterned tail.