Back to Mountain Stone Home Mountain Stone® River Rock | Classic Series Water-worn smoothness. Ageless charm.Coverage areas are based on 1/2″ mortar joints. Coverage will vary based on joint size, cutting, or trimming preference by the mason. Stone sizes: 5″-9″ in diameter. Thickness range is 1″-2.5″ River Rock Cut Sheet Gallery Colors Antique Grey Ozark Sulfur Springs