Wilson 1½" x ¾" Railroad Ballast is a clean, crushed granite. This Ballast isproduced daily at Wilson Quarry to meet the American Railway EngineeringAssociation (AREA) #4 Ballast Specifiions as well as ASTM C33 Size #4. Thisproduct has been used by the Railroad as Ballast Aggregate since the late 1800's. Thistype of rock is typically gray in color.