Abstract

Brookite-bearing sandstone near Gallup, New Mexico, was found by a Navajo Indian while prospecting for uranium. Owing to its high content of zircon the radioactivity of the sandstone is about 3 to 5 times above background. Though it was first considered as "uranium ore" by the prospector, the sandstone was referred to locally as the "Gallup titanium deposit" after titania minerals were found to be the important constituents of the sandstone. The light minerals of the sandstone include albite, orthoclase, and quartz. The heavy minerals include anatase, apatite, brookite, ilmenite, magnetite, rutile, spessartite, sphene, tourmaline, and zircon. The clay minerals include kaolinite, montmorillonite, and limonite. Leucoxene has formed at the expense of ilmenite. Authigenic brookite, which occurs mostly as small boxworks between other detrital mineral grains, formed at the expense of both ilmenite and leucoxene. Detrital rutile was not positively identified.

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