Hoshizuna no Hama (“star sand beach”) is a small beach located on a remote island in Japan. The grains of sand found here are shaped like tiny stars. It’s not really sand but the exoskeletons of tiny one-celled organisms, called Baclogypsina sphaerulata. – WTF Fun Facts
Source: The Star Sand Beach of Hoshizuna-no-hama | Amusing Planet