These gorgeous treads are sawn out of bronze basalt columns and have one long natural crust edge and one long/two short edges that are black split face. So, you have a choice of which edge to expose for a natural contrast or more formal look.
The surfaces of each tread are thermal finished.
All 6 1/2" thick x 36",48",60" and 72" lengths x approx 16" depth. Depth will vary slightly due to the organic edge and its natural variation.