Hoshizuna no Hama is a small beach located on the northern tip of the remote Iriomote Island in Okinawa Prefecture, in Japan. Hoshizuna no Hama means “star sand beach”, and is so named because the grains of sand found here are shaped like tiny stars. These are not really sand but the exoskeletons of tiny one-celled organism, barely a millimeter across, called Baclogypsina sphaerulata that live among the sea grass.

Baclogypsina sphaerulata is a protozoa belonging to the family Calcalinidae. Their exoskeleton (or shell) is shaped like a star with 5 or 6 pointed spines or arms that help them move from place to place and also store some of the diatoms that they feed upon. The outer shell is made of calcium carbonate, and when they die, they leave their star shaped exoskeleton behind to be washed up on the beaches in enormous numbers.

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