A trace radioactive element, symbol, Ra. It occurs in uranium ores
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Tag: <span>R</span>
Marine protozoa subject to silica replacement fossilization sound in limestone, shale and other rocks
Lines converging at a single center
Alpha, beta or gamma energy emitted by the decay of atomic nuclei from their radioactive source
An ore or arsenic, Arsenic monosulfide.
A heavy, dense, rare element of the platinum group. Symbol, Rh
Rare mineral and metallic elements such as niobium, yttrium, Lanthanum, cerium, praseodymium, neodymium, samarium, thulium, ytterbium, neodymium, dysprosium, gadolinium, promethium, scandium and lutetium
A fine-grained, extrusive igneous rock, having parallel mineral composition with granite
A shaft or room that has been excavated from the ground upward
A heavy, dense and rare, silvery-white precious metal. Symbol, Re