Estimated coverage: Boulders - 12.5 sq ft per ton 8" - 20" Mini Boulders - 45 - 65 sq ft per ton 4" - 8" Cobbles - 65 - 75 sq ft per ton. ... Black Granite - $339.00 per ton OR $0.17 per pound. Colorado Moss - $331.00 per ton OR $0.166 per pound. Copper Creek Onyx - $760.00 per ton OR $0.38 per pound.