Honed marble 3" hexagon mosaic in 'Jet Black'
https://www.subwaymosaics.com/shop/mmbh3hf-honed-marble-3-hexagon-mosaic-in-jet-black-10073
https://www.subwaymosaics.com/web/image/product.template/10073/image_1920?unique=4267645
Sold in individual 0.85SF sheets.
Standard 3/8" thickness.