Siderastrea siderea is a colonial coral that forms low domes or boulder-shaped structures with a smooth dimpled surface as much as 2 metres (6 ft 7 in) wide on the seabed.

[3] The corallites, the calcareous cup-shaped depressions in which the polyps sit, are about 5 millimetres (0.20 in) wide with about 50 or 60 little ridges called septa.

This species can be confused with the closely related lesser starlet coral (Siderastrea radians) but that is usually smaller and has deeper, more angular corallites, each with 30 to 40 septa.

[3] Siderastrea siderea is found in the Caribbean Sea and the northern Gulf of Mexico and round the coasts of southern Florida, the Bahamas and Bermuda.

In a study, cores were drilled and samples taken from the coral in different zones in order to determine whether rates of growth had changed over the last hundred years.