Star sand is marine sediment composed of star-shaped particles. Despite its name, star sand is a collection of shells of dead foraminifera, and differs from ordinary sand derived from the weathering of rocks.

Because of the geometrical shape of their shells, which are reminiscent of stars, foraminifera in the genus Baculogypsina are widely appreciated not only as objects of biological study, but also as decorative ornaments.

星の砂 - 出典: フリー百科事典『ウィキペディア（Wikipedia）』