A. Not really. It should have an opening within that’s large to properly fit the Mezuzah scroll they will be using. Also many Mezuzahs have the Hebrew Letter Shin on the outside, but this not an absolute requirement. And it should be affix-able to a doorpost, being made of stone may make it a heavier cover and some consideration should go into how it will be affixed (holes for nails or other connectables). Jewish tradition encourages us to beautify our observances, and this personal gift is surely a way to do it.