Phlogopite mica surfaces have been observed under various conditions by an atomic force microscope (AFM). Although the AFM images change with the scan directions, we suppose that the hexagonal arrays which appeared in the AFM images are oxygen atoms from the observations of phlogopite mica surfaces after an ionexchange. Similar periodic structure images were obtained in water and in silicone oil as well as in air. Particularly clear images were obtained in pure water.