The cards printed at cartamundi are usually printed on the so called “Corona” cardstock. This special cardstock has a blue layer of graphite to give the card it’s snap. This special paper is usally refered as bluecore paper.
Since it is not available on the open market, counterfeits are mostly printed on white or blackcore paper. If you rip a fake apart you can check the color of the inner layer. If it is not blue, the card is most likely fake but your card will be destroid.
A problem with this test is that there were actually real magic cards printed on blackcore paper as well, they are rare but they exist.