Tenebrescence is an optical phenomenon, seen in the mineral hackmanite and some others, which resembles phosphorescence. The main difference between phosphorescence and tenebrescence is that the former is a glow-in-the-dark, while in the latter case, the stone needs light to show its temporary color.

The term is derived from the Latin word for darkness. The term tenebrism is applied to paintings of the Italian Renaissance painter Carravaggio where the figures are dramatically lit by unknown light sources.