Given a passage and a query based on the passage, generate an unambiguous, concise and simple answer to the query from information in the passage. Note that the answer may not be present in exact form.
Q: This material has been used ever since ancient times and has formed all over the world. Thanks to these stones, building materials of great quality can be formed, and they are mainly used as they are lightweight yet strong. Other buildings made out of oolitic limestone are The British Museum and St. Paul's Cathedral. Oolitic limestone was used to build the Pentagon as well as other buildings around the world, such as Buckingham Palace and the Empire State Building. Scientists have discovered that oolitic limestone is actually a material which was made out of microbes that existed 200 million years ago, at the time of the Jurassic era when dinosaurs were still present on the Earth. OOLITIC LIMESTONE. Oolitic limestone is a carbonate rock made up mostly of ooliths (or ooids) which are sand-sized carbonate particles that have concentric rings of CaCO 3. These rings are formed around grains of sand or shell fragments that were rolled around on the shallow sea floor, gathering layer after layer of limestone. How did oolitic limestone form? Previously, scientists thought that the ooids formed from grains rolled on the seafloor and then accumulated layers of sediment. "Oolitic limestone is a carbonate rock made up mostly of ooliths (or ooids) which are sand-sized carbonate particles that have concentric rings of CaCO3. These rings are formed around grains of sand or shell fragments that were rolled around on the shallow sea floor, gathering layer after layer of limestone," University College London gave an explanation on its website. Limestone is by definition a rock that contains at least 50% calcium carbonate in the form of calcite by weight. All limestones contain at least a few percent other materials. These can be small particles of quartz, feldspar, clay minerals, pyrite, siderite, and other minerals. Limestone is a sedimentary rock composed primarily of calcium carbonate (CaCO 3) in the form of the mineral calcite. It most commonly forms in clear, warm, shallow marine waters. It is usually an organic sedimentary rock that forms from the accumulation of shell, coral, algal, and fecal debris. Limestone is a sedimentary rock comprising at least 80% calcium carbonate (CaCO3). Limestones can be deposited in both marine and fresh water environments, the former being more common, and can take many forms such as those described below. Chalk is a pure, soft, well-jointed limestone composed primarily of the calcareous remains of micro-organisms called coccoliths and foraminifera. Pure white chalk contains more than 90% CaCO3 and is usually found in thick beds. In Britain it stretches from Yorkshire down to the famous cliffs of Dover. oolitic limestone Oolitic limestone is a carbonate rock made up mostly of ooliths (or ooids) which are sand-sized carbonate particles that have concentric rings of CaCO 3. These rings are formed around grains of sand or shell fragments that were rolled around on the shallow sea floor, gathering layer after layer of limestone. Portland limestone is an example of an oolitic limestone. This limestone formed in a shallow sea, rather like the modern Bahamas, near the end of the Jurassic period (~135 million years ago). The rock has an even structure rather like cod roe and it can therefore be cut or sculpted in any direction. Oolitic Limestone: A limestone composed mainly of calcium carbonate oolites, small spheres formed by the concentric precipitation of calcium carbonate on a sand grain or shell fragment. Travertine: A limestone that forms by evaporative precipitation, often in a cave, to produce formations such as stalactites, stalagmites, and flowstone. Query: how is oolitic limestone formed
A:
Oolitic limestone is actually a material which was made out of microbes that existed 200 million years ago.