Wood Plank Found on Mars?

I don't think urban legends are being spread by email as much lately, but if you see something about a wood plank found on Mars Universe Today reports it's not wood. Here's the real picture in question.

And here's the explanation, "'What you're seeing is a piece of flat, platy, layered sulfur-rich outcrop rock like we've seen almost everywhere the Opportunity rover has been in Meridiani Planum,' said Bell. 'Sometimes, like in this case, those flat, platy rocks have been tilted or dislodged, this one probably from the forces associated with the huge impact crater that formed nearby.'"