Brown, yellow, orange, and greenish-black thorites from the Seerie pegmatite, Colorado

Journal of Research of the U.S. Geological Survey
By: , and 

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Abstract

Four types of thorite  - brown, yellow, orange, and greenish-black - occur together in narrow fracture fillings rich in brown fluorite near the outer edge of the Seerie pegmatite. The brown thorite is by far the most abundant. The thorites are remarkably similar in composition except for their Fe2O3 and UO2 contents. The common brown thorite contains about 5 percent Fe2O3, but the other types have only about 0.3 percent. The greenish-black thorite contains about 15 percent UO2; the yellow and orange, about 7 percent; and the brown, about 3 percent. All four thorites have high total rare-earth oxide contents, which vary from 17.3 to 20 percent. The rare-earth assemblage is unusual in that the heavy rare earths predominate, ytterbium being the most abundant lanthanide. Unheated brown and yellow thorites gave thorite X-ray patterns, but the orange and greenish-black types are metamict. All the thorites gave a ThO2-UO2 X-ray pattern as well as a thorite pattern after heating in air for 1- and 2-hour periods at 1,000°C. In addition, the pattern of the greenish-black thorite contained peaks which we ascribe to a second UO2 compound. Minute black inclusions present in the greenish-black thorite were identified as uraninite by microprobe analysis.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Brown, yellow, orange, and greenish-black thorites from the Seerie pegmatite, Colorado
Series title Journal of Research of the U.S. Geological Survey
Volume 4
Issue 5
Year Published 1976
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Description 8 p.
First page 575
Last page 582
Country United States
State Colorado
County Jefferson County
Online Only (Y/N) N
Additional Online Files (Y/N) N