Black Mountain Stone - family room Living up to its name, Mountain Black is available in the grandest of scale. Each tile measures approximately five square feet. Mountain Black varies in color from charcoal black to shades of night with highlight of autumn brown. This stone is composed primarily of mineral quartz and sandstone. A wonderful rough surface due to the method of splitting the stone along its natural plane; this finish is referred to as a cleft finish or surface, adding texture and depth. Black Mountain has “sister” stones: Mint and Autumn Brown. These large flagstones are suitable for interior and great for exterior use in most areas.