Magnetite has been very important

Magnetite has been very important in understanding the conditions under which rocks form. Magnetite reacts with oxygen to produce hematite, and the mineral pair forms a buffer that can control oxygen fugacity. Commonly, igneous rocks contain grains of two solid solutions, one between magnetite and ulvospinel and the other between ilmenite and hematite. Compositions of the mineral pairs are used to calculate how oxidizing was the magma (i.e., the oxygen fugacity of the magma): a range of oxidizing conditions are found in magmas and the oxidation state helps to determine how the magmas might evolve by fractional crystallization.

Small grains of magnetite occur in almost all igneous and metamorphic rocks. Magnetite also occurs in many sedimentary rocks, including banded iron formations. In many igneous rocks, magnetite-rich and ilmenite-rich grains occur that precipitated together from magma. Magnetite also is produced from peridotites and dunites by serpentinization.

Magnetite is a valuable source of iron ore. It dissolves slowly in hydrochloric acid.



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Though Jones initially led the band, Jagger and Richards took over after teaming as the band's songwriters. By 1969 Jones had contributed minimally to recording, was legally barred from touring the United States, and was in failing health. By mutual agreement Jones left the band, and Mick Taylor became his replacement. Weeks after leaving the band, Jones drowned. Taylor left in 1974 and was replaced by Ronnie Wood. Wyman left in 1990, and his replacement Darryl Jones became the primary bassist, but he is not a full member. Stewart was taken from the official lineup in 1963 to continue as the band's road manager and occasional keyboardist until his death in 1985. Chuck Leavell has been the primary keyboardist for the band.

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