When they reproduce by splitting, each new cell gets one of the parts. They also tend to live in colder water, but since they photosynthesize, they of course are restricted to shallow water where the sunlight is. Their tests, when they accumulate on the bottom in great numbers, form Diatomaceous Ooze. A fossil Diatom A fossil Diatom. Evaporites are formed by the evaporation of seawater.
Manganese nodules form in certain areas on the ocean floor.
They are composed of manganese oxide with significant proportions of cobalt, iron, copper, magnesium, and other metal oxides as well. They accumulate VERY slowly. Oolites are generally formed by inorganic precipitation of calcium carbonate in warm, shallow waters such as are seen around Bermuda and the Bahamas. Most of them are thought to come from the Asteroid Belt, and are around 4.55 billion years old, the same age as the solar system. They are essentially debris left over from that formation that never accumulated into planets.