Stone & Pewter Accents Agate is a state-of-the-art mosaic glass tile collection with a look amazingly similar to natural layered silica created by volcanic stone formations. Agate is offered in two finishes, iridescent Pearl and matte Silk. The collection includes the new “Martini” shape, which, in the words of designer Carl Steadly, “has an interesting hexagonal shape that at first glance, looks like a martini shaker!”