@neenjax , Samsung , See the links below for guide on how to replace the back glass on Samsung Galaxy S6(rated as a difficult repair in the guide) and a couple links to where the glass can be purchased, which you can also do a search on for better pricing perhaps. Always insure part and color is correct for your model prior to ordering. Good luck. I hope this helped you out, if so let me know by pressing the helpful button.
[guide|44646]
https://www.google.ca/search?q=Galaxy+S6+rear+glass+replacement&oq=Galaxy+S6+rear+glass+replacement&aqs=chrome..69i57.10895j0j1&sourceid=chrome&ie=UTF-8
https://www.amazon.com/Battery-Adhesive-Preinstalled-Samsung-G920P/dp/B010JEQZYG