• journal_title：Mineralogical Magazine
• Contributor：R. L. Frost ; M. L. Weier ; G. A. Ayoko ; W. Martens ; J. Čejka
• Publisher：Mineralogical Society of Great Britain and Ireland
• Date：2006-
• Format：text/html
• Language：en
• Identifier：10.1180/0026461067030333
• journal_abbrev：Mineralogical Magazine
• issn：0026-461X
• volume：70
• issue：3
• firstpage：299
• section：Articles

A uranopilite from The South Alligator River, Northern Territory, Australia, has been studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) with EDAX attachment, and thermogravimetry in conjunction with evolved gas mass spectrometry. The XRD shows that the mineral is a pure uranopilite with few if any impurities. The SEM images show that the uranopilite consists of elongated crystals, up to 50 μm long and 5 μm wide. Thermogravimetry combined with mass spectrometry shows that dehydration occurs at ~31°C resulting in the formation of metauranopilite. The first dehydration step over 20–71°C corresponds to a decrease of 5.4 wt.%, equivalent to 6.076 H₂O. The second dehydration step, over the temperature range 71–162.4°C corresponds to a decrease of 4.7 wt.%, equivalent to 5.288 H₂O, making a total of 11.364 moles of H₂O, close to 12 H₂O for uranopilite.

Dehydroxylation takes place over the temperature range 80–160°C. The loss of sulphate occurs at higher temperatures in two steps at 622 and 636°C. A mass loss also occurs at 755°C, accounted for by evolved oxygen.