So it seems that my unzan stone is currently deteriorating, and is losing coloration. I realize it is advertised as a "processed stone," however, after roughly 6 months of ownership several areas of the stone have now faded from the rather dark black/brown it arrived as, into a very light brown. Think dry dirt. I wanted to verify this was not just an accumulation of sediment or algae and used a metal tool to scratch one of the discolored areas. When I dig into the stone with a metal tool it seems the lighter color may be the actual underlying color of the stone. Highly disappointing considering the cost. Has anyone else experienced this?