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.
Titanium deposits that can be mined economically are found throughout the world. The main ores are rutile (TiO2) and ilmenite (FeTiO3) in beach sand deposits (Western Australia), ilmenite-haematite (Canada), and ilmenite-magnetite (Ukraine) in hard rock deposits (Figure 5).