I had no idea!…
Did you know that cutting mats can shatter?! I sure didn’t… until now that is. One of the days when we were loading a truck to move things from my old place in the mountains (we’re here in Colorado) to my new home, it was 6 degrees below zero. I was inside the house packing and the guys were carrying things out to the driveway and loading the truck. Apparently my mat was hanging out on top of a pile of boxes. And when most of the truck was loaded my mat got tossed up onto the boxes in the truck. A photo of the remains appears below. When the truck was empty I swept out the pieces and put them together like a puzzle so I could snap this photo. I guess mats don’t appreciate really harsh temperatures. Poor thing.
The silver lining is that now I have a new, unblemished, non-stained mat!
Tomorrow is Saturday, so the unpacking will continue in earnest. I keep forgetting to take photos as I fill my shelves, but I won’t forget this weekend. I’ve been trying something new, so it’ll be interesting to see if it works out. More on Monday 
Those mats will melt too. Years ago when attending Festival in Houston I saw one melted to the rug in a car’s hatchback. The owner put it there to keep it flat. Picking up a corner reminded me of freshly chewed gum.
At least you matt was an easy clean up.