Flagstone Idaho Cherokee Charcoal Quartzite Select (Coping) 2 1/2 - 3 in.. Idaho Cherokee Charcoal Flagstone is a natural stone featuring deep grey and black tones complemented by streaks of earthy charcoal. This quartzite brings a sense of depth and elegance to any space, whether indoors or as an outdoor accent. These select coping pieces are hand selected to have consistent thickness to be used on the edge of a pool or spa or as a coping on a retaining wall or step.