Geology: Neobium solution

As the Earth's core separated from the mantle, elements were distributed according to their affinities for the metallic core and the silicate mantle. Hence the mystery of Earth's 'missing' niobium. Niobium, the thinking went, is a 'lithophile' (or 'rock-loving') element and so should be present in the mantle in proportions, relative to the other elements, similar to those seen in the stony meteorites that record the make up of the early Solar System. The fact that there is less niobium in the crust and upper mantle than expected led to the suggestion that there were niobium-rich reservoirs hidden deeper in the mantle. But a new look at niobium's properties reveals that at high pressure it partitions between liquid metal and silicate in just the same way as the siderophile (iron-loving) element vanadium. So the niobium may have been in the core all along.

The Earth's 'missing' niobium may be in the core
J. WADE, B. J. WOOD
Nature 409, 75-78 (4 January 2001)
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earth : Earth scientists iron out their differences
Two groups of geochemists suggest elementary solutions to some mysteries of the Earth's mantle. (4 January 2001)

4 January 2001 table of contents