Coral polyps also use the energy supplied by their symbiotic algae to produce calcium carbonate, or limestone. They secrete the limestone from their base, creating a protective skeleton and a hollow chamber called a cup. The polyps retreat into their cup to hide when predators come looking for them.
Uranium is mined where there are concentrations in the earthâs crust. More than half of the worldâs uranium comes from mines in Canada, Australia and Kazakhstan.Other major producers are the United States, South Africa, Namibia, Brazil, Niger and Russia.Many more countries have smaller deposits that could be mined if needed.ore than half of the worldâs uranium comes from mines in Canada, Australia and Kazakhstan. Other major producers are the United States, South Africa, Namibia, Brazil, Niger and Russia. Many more countries have smaller deposits that could be mined if needed.
Neodymium is never found in nature as a free element, but rather it occurs in ores such as monazite and bastnÃ¤site that contain small amounts of all the rare earth metals. The main mining areas are in China, the United States, Brazil, India, Sri Lanka, and Australia.