STAR SAND
Star sand is a biogenic "sand" made of the star-shaped exoskeletons of tiny, single-celled sea creatures belonging to the Foraminifera group.
Foraminifera, Latin for "hole bearers", are single-celled organisms, members of a phylum or class of amoeboid protists characterized by streaming granular ectoplasm for catching food and other uses; and commonly an external shell (called a "test") of diverse forms and materials.
Most foraminifera are marine, the majority of which live on or within the seafloor sediment, while a smaller number float in the water column at various depths are planktonic. Star sand is considered planktonic foraminifera.
This sample is from Ishigaki Island in Okinawa, Japan. This type of sand can only be found on a few beaches in the world.