My friend (who lives in a warm, humid climate) often has issues with chocolate, due to the formation of a light-colored coating on it. I believe it is just chocolate bloom, but she thinks it's mold and should trash the chocolate. Visual inspection alone does not seem sufficiently precise to identify which of these has happened.
Is there a reliable way to test which one is the case? i.e., re-heating it, or trying to remove the coating with a knife, or some other technique which does not require using a microscope?