Turned out there were only two different types of inclusions and most were too deep in the stones to get a sharp image at higher mag. However, the one featured in the first pic had some inclusions near the surface that captured OK. I used a 20x Mitty pushed down to 13.5x onto APS-C to take a stack of 140 images. Zerene PMax stereo with no retouching.
No earth shattering result, but a very interesting interlude for just £1 spent - and I'm left with several potential "tiny insect mounts" for use in future studio macros too. Winner

The jar of stones 13.5x closeup of one inclusion