Is calcium carbonate a polar covalent compound?

CaCl2 is an Ionic molecule. With Electronegativities of 1.00 and 3.16, a difference of 2.16, this falls into the category of Ionic Bond.

The scale I have always used is 0-0.39 Non Polar Covalent, 0.4-1.79 Polar Covalent and 1.8 and Up Ionic. If you have a sample to test, you could heat it on a hot plate, Ionic compounds don't melt too well, you could also dissolve it in water as ionic compound typically dissolve well in water.