The acid test, over time, well, they all dissolved, and while I'd set up my camera to do some time lapse photography it wasn't in a convenient location, the light sources varied, overall not a success. But I've learned, mebbe, and next time it'll be better. Meanwhile, a few photos of the vanishing implausible shapes and impossible lustres ...
2 rather well formed pyrope garnets, the one on the left orange, on the right deep red/purple. Not diamonds...
Playing with light sources, over time the pebbles grew smaller and smaller, not diamonds...
Pink garnet dissolving on the right...
and a fingernail full of dissolving garnet...
All the indications are right, the associated minerals are there, but I'll need to dig a bit deeper, and an awful lot more, moving upstream all the while...
I've the entire summer...