How to tell real black onyx from glass. I've recently been conned and should have known better! As a savvy merchant, I am always on the look out for better prices - like we all do. However, quality is the most important thing to us and the stone being real is paramount! So, what happened recently is worthwhile sharing. The adage stands true - if something is too good to be true, it likely is. I was buying this site unseen and their website listed stones that were imitation as well as real stone strands that were just a bit cheaper than my current source, but not by a lot. Also, they only make these rounds, so it was conceivable that their prices are lower - economy of scale! So, I bought stones, thinking that it would be safe that they are real. Black onyx is harder than other stones to tell if it is real just by eyeballing, but I became immediately suspicious. There are some telltale signs that the strands are glass: the tops of beads had slight dimple - common with lamp work beads; the strands were not as cold as some of my stone strands (glass never gets as cold as stone); and it looked different when I smashed one of the beads open and compared to one of stone. The glass bead was much shinier than the stone and the break patterns were completely different and reminded me of broken glass. I have learned my lesson and will go back to my trusted source for any online purchases, otherwise, I will have to see and test first. I hope this story has been beneficial to you.