Star sand

Star sand (Japanese: 星砂, romanized: hoshizuna, lit. 'star-sand'),^[2] also known as living sand,^[3] is a rare sand-like substance made up of the star-shaped skeletal remains of marine foraminifera in the family Calcirinidae.^[4][5][6][7] When the Calcirinids die, their skeletons are swept from their reef habitats and accumulate by the billions on shore.^[8] A Japanese myth holds that grains of star sand are the skeletons of descendants of the North Star and the Southern Cross, fallen to the waters of Okinawa and killed by a serpent sent by the god of the sea.^[5] Star sand is found on shores throughout the west and south Pacific, including in the Indonesian archipelago, the Okinawa Islands, and Raine Island.^[5][9][10] Development of star sand causes beaches to "grow" over time as a result of the forams' life cycle,^[5] with annual rates of calcium carbonate production as high as 1 kg/m² near coral reef margins in the Pacific.^[3] Because of this, laboratory production of star sand for beach renourishment has been developed in Japan.^[11][12] The Japanese government has cultured star sand at Okinotorishima to build the islet into a more stable atoll and thus to strengthen Japan's legal claim to the surrounding waters, which otherwise would belong to China.^[13][14] Up to three quarters of the sediment mass of Tuvalu is star sand.^[15] Bottles of star sand are sold as souvenirs.^[9][3] Arenophiles acquire samples of star sand through trade with other enthusiasts.^[16] Collection of large quantities of star sand for commercial purposes from the Great Barrier Reef is prohibited.^[17] Since 1979, the erosion of individual grains of Baculogypsina sphaerulata star sand has been used as a metric of littoral drift in Japan, with scientists using the lengths of the skeletal spines to reconstruct the origins and travel distances of sediment deposits.^[18][2] A similar process of measuring star sand spines was used in 2012 to study depositional processes on Raine Reef in the Great Barrier Reef.^[19]

Magnified star sand found in Okinawa

Yurigahama beach on Yoronjima is famous for its star sand^[1]

See also

• Conchology