由于萤石(CaF_2)的钙离子半径(1.06)与钍离子半径(1.10)、特别是与四价铀离子半径(1.05)相似,所以铀和钍常常置换萤石中的钙而进入萤石晶格。此外,铀和钍还能以吸附形式赋存在萤石裂隙中或其表面上,或者成为独立的矿物以固体包体形式存在于萤石中。因此,萤石常含有铀和钍,加之周围岩石中也经常含有放射性元素,从而形成了放射场。萤 Because CaF 2 has a calcium ion radius (1.06) that is similar to the thorium ion radius (1.10), especially to the uranium ion radius (1.05), uranium and thorium often displace calcium from fluorite to fluorspar grid. In addition, uranium and thorium can also be present in adsorption form in or on the surface of fluorite fractures, or as separate minerals in the form of solid inclusions in fluorite. Therefore, fluorite often contains uranium and thorium, coupled with the surrounding rock often contains radioactive elements, thus forming a radiation field. firefly