The corners are actually made of the same material at the rest of the cover. The material appears to be molded or bent over to hold the iPad. If you've seen a Marware C.E.O. Hybrid, it's the exact same fastening system. The material in the corners are thick and should provide excellent protection for the device's corners. I don't think it will scratch the mini but I've only had ours for a few days now. Over time "scuff" marks may develop, but I doubt that it will cause actual scratches.
No scratches that I can notice. The case seems to be hard plastic sandwiched between leather (outside) and a suede type leather on the inside (think suede couch). I am satisfied with the protection and fit is good esp. for the price!