Montreal is a tumbled castle rock style thin stone veneer.  The stone is predominantly grey with just a hint of brown and tan mineral staining.  The tumbling process gives Montreal an aged or antiqued appearance.  The individual pieces of Montreal are split with a hydraulic press on all four sides to create the rectangles characteristic of the castle rock style.  The splitting process leaves relatively sharp 90-degree edges on the stone.  The edges of the stone are then softened and slightly rounded by the tumbling process. The pieces grind against each other in the large drum tumbler during tumbling which also softens the face of the stone for a smoother texture.