Dark-Field Lighting 2
Strobist info: (also see graphic below in comments) the base is a piece of black opaque glass with a black foam core background. Light from a strobe is passing through a white diffuser (white sheet) and coming from the sides of the foam core. Foam core gobos on the left and right to let just a sliver of light on both sides.
Also see my DIY Fake Ice Cubes tutotrial.