I don’t know what it is but I have to stare at it all day 
There’s a label that says the wood has been treated with copper azole wood preservative but I’m not sure what this stain is, how do I clean it off without damaging it?
I don’t know what it is but I have to stare at it all day
There’s a label that says the wood has been treated with copper azole wood preservative but I’m not sure what this stain is, how do I clean it off without damaging it?
OP, I actually do woodworking as a hobby. A couple posters are correct that this is the copper treatment to make it not rot. Sometimes in the pressure chambers the chemicals concentrate in a spot, or the wood can absorb it more in one area. You can sand it off, but please wear a mask and eye protection every time you create sawdust. Even without the chemicals in it, sawdust is horrible for your lungs, and the smallest fleck in your eye can ruin your entire day. A less hazardous way to get this off is with a hand plane, but it takes a bit of experience to use it and blend it all together well.