Took a bit of thinking to work out how to do this, but in the end was simple to setup.
There is a sheet of black Fun Foam on the table which acts as the background.
The white marble is sat on a short tube about 2inches/50mm long (from the centre of a till roll) which holds it clear of the surface and remains hidden under the marble.
Lighting is coloured in the same way as yesterday, with a blue plastic bag over a screen of tracing paper, with the lights behind.
Two lights are used to illuminate the screen. The first a 20watt stick type CFL in a Pringles tube reflector, to light up the whole screen.
The second an 11watt spiral type CFL in a Pringles tube snoot to give a hotter spot on the screen.
Combined together, they provided the graduated effect that can just about be seen, despite the flash used here.
There was also an A4 sized white reflector to add a bit of fill light to the shadow side, which was removed for this setup shot.

A simple DIY light table made from a cardboard box. The inside of the box is in white cardboard, which makes life a lot easier. The end where the light is positioned already had a cutout for removing the biscuits/cookies when sat on a shop shelf, so the only modification was to cut an opening in the removeable lid.
Over this is placed a slightly opaque plastic document box, which I often use as a stand up diffuser. A sheet of tracing paper is placed inside to even out any hotspots from the light.
The mask on top is a single sheet of black card with a cicular hole cut out of it. The eagle eyed will also see an extra strip of card on the right, which was added to prevent a bit of flare on the camera lens.
The light is provided by a single 20watt stick type CFL bulb in a Pringles tube reflector, which just happened to fit the opening in the box perfectly ;-)