Hi, I’m not in the timber trade, but I just purchased some cut lengths of European Oak. On arrival, it’s a bit wet (rain storm), but some planks have quite a notably thick black substance on them. I’m not sure if this is some form of storage protection or a mould. It feels soft to the touch. Hopefully a photo attached. Can anyone advise what this might be and how best to clean it up, I want to get to the natural look. I intend to treat with Osmo UV protection oil extra clear, so the black finish needs to go. 

thanks in advance