how to identify whether vintage jet or black glass buttons

[onekiwi0]

at a fair I purchased a small packet of very old buttons.  I say very old as the part packaging was crumbling. and some pearlised ones were peeling off their tops.. I am assuming these would be black galss as opposed to jet?  any way to identify?  they're still very pretty.  just curious...I think I might keep for my own collection rather than sell... thanks

[debra9275]

With genuine jet, if you have an old tile lying around, scrape the jet on the back of the tile and it will leave a charcoal like brown mark. That's the only way I know to tell the difference... A lot of jewellrey etc. Is called jet although it actually isn't. I think from looking at your pic, that the buttons could be glass