The
X-Ray where I work has supplier provided calibration pieces of glass, ceramic, rubber, aluminium and stainless steel of varying sizes. I have never had a failed or incomplete result for the glass calibration piece. Also keep in mind X-Rays detect by density so even things along the lines of fruit seeds come up looking like a small black stones in your product which will cause the
X-Ray to reject it. Yes settings could be adjusted to stop this but I would rather be safe than sorry!
I would recommend talking to suppliers of
X-Ray machines, they would be able to give you the best answers as to what would be suitable for glass detection in your product(s).