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A trace radioactive element, symbol, Ra. It occurs in uranium ores

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

The closing and rehabilitation of a mine back to its original or natural state

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