. The tetraboride was first reported as being synthesized directly from the elements in 1960 by three independent groups: Carl Cline and Donald Sands; Ervin Colton; and Cyrill Brosset and Bengt Magnusson. It has been proposed that the triboride is a silicon-rich version of the tetraboride. Hence, the stoichiometry of either compound could be expressed as SiB where "x" = 0 or 1. All the silicon borides are black, crystalline materials of similar density: 2.52 and 2