Black Granite Landscape Boulders Granite and Granite Gniess Materials California rock quarries We hand select these black granite boulders from quarries and construction sites as available. Black granite boulders are really difficult to come by as an affordable landscape material. It is usually easier to use black / gray basalt or other rock materials. We have a limited amount of black to gray black granite boulders from 12 inches to 6 feet available. These materials can ship as palleted material anywhere as needed. Academy Black Granite bouldes are not part of this group of material. These boulders are great for landscaping. The color ranges from strong salt n pepper to black grey colors.