Here's the setup I used (thanks to PuzzledPaul and Rik for the ideas:

That's one of my daughters, Emily, who was eager to help me out. I used my tripod connector to move my camera between the two blocks of wood and a troublelight for lighting. I also used a remote shutter release so I didn't jar the camera.
The result is a stack of 12 images (moved about .5cm each pic) that I stacked in HF (note the watermark text as my copy has already expired). You can see the troublelight in the reflection of the garnet stone in the centre, but that's fine for testing purposes:

Canon EOS 300D
EF-S 18-55mm with +4,+2,+1 closeup lenses
ISO 100
F16
1/3s