First guess: "oolites"
First guess: "oolites"
http://en.wikipedia.org/wiki/Oolite
They are usually formed in warm, supersaturated, shallow, highly agitated marine water intertidal environments,though some are formed in inland lakes. The mechanism of formation starts with a small fragment of sediment acting as a 'seed', e.g. a piece of a shell. Strong intertidal currents wash the 'seeds' around on the seabed where they accumulate layers of chemically precipitated calcite from the supersaturated water.
(edited with link and quote)