oölite

Oölite is a sedimentary rock composed primarily of oöids, which are spherical or subspherical grains formed by the accretion of calcium carbonate or other minerals around a nucleus, such as a shell fragment or a sand grain. These oöids are typically between 0.25 and 2 millimeters in diameter. The term oölite is derived from the Greek word "ōión," meaning egg.

Oölitic limestones are the most common type of oölite. They form in shallow, warm marine environments, often in areas with strong currents or wave action that keep the oöids in constant motion, allowing for uniform accretion. The formation process involves the precipitation of calcium carbonate from seawater onto the nucleus. Other minerals, such as dolomite, chert, or iron oxides, can also form oölitic structures.

Oölitic rocks are often recognizable by their distinctive pisolitic texture, resembling a collection of tiny eggs or peas. They can vary in color depending on the cementing material and any impurities present, ranging from white and gray to pink and brown. Oölites are found in various geological settings worldwide and can be important sources of building materials and reservoirs for oil and gas. Their formation conditions can also provide clues about past environmental conditions.