PETRA CONCRETE QUARTZPetra Concrete Quartz is a peculiar grey quartz with a dark grey background and light grey patches all over the surface. The stones are matt finished, sturdy and rigid stone which will be perfect as worktops and countertops. Quartz stones don't need a lot of maintenance, but the engineered stone still needs some basic care and upkeep to appear beautiful. Both natural and engineered stones require your time and attention to maintain their luster and