Hi Ralph. I bought several boards like this at a local antique/craft shop. One of the booths has various kinds of air dried lumber. I think the color may be due to how it was dried, maybe some fungus causing some spalting in the area that l used as land. I guess a better answer would be, I don't really know. I got around 6 boards for $20 so it's dirt cheap, but it has some beetle holes in it so I have to deal with making sure they're taken care of/dead. I heat it up to 140 degrees for a couple of hours in the warming drawer on our oven.