Are all faces of the cube intact? Given that it is probably a paperweight, could it have been drilled and loaded with lead? (with the hole being plugged with a nearly matching disc of the same stone)
Me too! Well, not most of my life, but maybe for a year or two after first encountering the word.
Gems and minerals have been a nearly lifelong interest of mine, and I was quite young when I first started reading books on the subject, like Herbert Zim’s Rocks And Minerals, where I first read about onyx. In most situations, I had absolutely no problems with dyslexia, but there’s something about that particular word that leads some people to misread it as “oynx”.
You’re describing agate. The only real distinguishing feature between onyx and agate is whether the bands are parallel or chaotic.
Like I said, this could be easily solved by a scratch test (or even better, an acid test) but only if the cube isn’t coated
And Spectre, don’t confuse the SG of a mineral for the SG of what you have there, which is a rock. Rock SGs can vary quite a bit from their component SGs - gas inclusions, voids, oxide content etc. all introduce variability.
And you’re not going to damage anything, except possibly a cube of halite, by a few seconds of immersion in tapwater…