Black stone is a medium for carving sculptural images. The primary figurative subjects represented are protectors and wrathful deities with occasional figures of siddhas and teachers. Sometimes sets of figures are created such as the example of Vaishravana Riding a Lion and the Eight Horsemen. For this example only three of the nine figures are currently known.
Black stone has been used for sculpture for over a thousand years and continues today. It is very difficult to distinguish a black stone carving from hundreds of years ago and a black stone carving made today from Eastern Tibet.
The Shadbhuja Mahakala shown at the left is one of the finest examples of a carving in black stone.