https://www.zgallerie.com/p-8438-agate-coaster-terra-set-of-4.aspx?source=myregistry
Buried treasure comes to Z Gallerie as dramatic Terra Agate coasters. This highly desirable stone, valued by artisans for decorative objects, is cut transversely to highlight the natural concentric bands and a rich natural Terra color. Agate is known for its density and resistance to acids, and is therefore ideal for use as coasters. Each piece is of a unique size and shape.