How can I tell if a water spot is a mineral deposit or clear-coat etching?

A mineral deposit sits on top of the surface and often feels slightly raised or rough, and it usually responds to acidic cleaning or a water-spot remover. Etching is a physical or chemical depression in the coating or clear coat and remains visible as a ring or crater after the mineral residue has been removed. Clean the area chemically first, then inspect under strong, angled lighting: whatever is still visible is likely etching.