Recently I purchased this very large bead (35x35 mm, with a 9 mm perforation) from a Chinese man, someone not particulary interested in beads. He didn't know a word about it, neither do I: it surely looks old, but do not know what material is it made of, where comes it from, or what culture it belongs to...
I post it hoping someone here can say something.

*what looks like tiny quartz crystals can be seen in the crack to the left with a magnifier.