??? "Crystals" would have been more than enough! I was about to award this to syphon for "polished stones" as the closest guess, even though they aren't polished, they are au naturale crystals. And then CL answers "crystals under polarised light" - which is exactly what they are! Wow - great detail mate!
I'll add some more information as a reward and for interest when you glance at my avatar (for as long as I have this one.) Three of the long crystals are all variations of topaz, while the green one is a pretty tourmaline. The purple ones are amethysts while all the rest are raw sapphires in blue, red and greenish yellow.
I think it is an interesting image, pretty and takes a bit of figuring out.
Thanks for your interest!
Cheers,
Sextus