Dia Mixed Color 4-5 Inches Natural Agate Coasters Gemstone Agate Beverage Coasters for Drinks Gift Set of 4 Formed when silica-laden groundwater passes through air pockets in cooling lava, agate is an exceptionally unique mineral that was once thought to protect its owners from danger and even produce delightful dreams. These agate coasters from southern Brazil, and while they may not bring you any dreams, they will bring beautiful nature and warmth into your home. Dia 4-5inch big size set of 4 100% nature