Thanks for your question! This backspash is glass.
I used a combination of an opalescent tile in varying sizes (Casa Dolce Casa, Neutra Vetro Glass Tile, Color: 03 Avorio Lux) with randomly inserted glossy glass tiles in the gray (Walker Zanger Spa Glass, Serenity Gloss Splash Liner). I used that to tie in the soapstone counters and get some added detail in the splash without it getting too busy.
Q
Similar granite
Q