Trap Rock. A Crushed Gravel with a mixture of dark gray, red, and maroon. Varying in size of 5/8″ to 3/4″. Trap Rock is an excellent replacement for dark mulch. Approximate coverage of 130 sf/ton. Broad Ripple, Carmel, Castleton, Cicero, Fortville, Geist, Greenfield, Hamilton County, Indianapolis, Lawrence, McCordsville, Morse Reservoir ...