Chemistry:Guilleminite

From HandWiki
Guilleminite
Guilleminite-Vandenbrandeite-Cuprosklodowskite-201031.jpg
A cuprosklodowskite vug filled with well formed dark green vandenbrandeite crystals. These are dusted over with small yellow crystals of guilleminite.
General
CategoryOxide minerals
Formula
(repeating unit)
Ba(UO2)3(SeO3)2(OH)4·3H2O
Strunz classification4.JJ.10
Dana classification34.07.03.01
Crystal systemOrthorhombic
Crystal classPyramidal (mm2)
(same H-M symbol)
Space groupP21nm
Unit cell869.48 Å3
Identification
ColorBright yellow, greenish yellow, yellow
CleavagePerfect on {100}, good on {010}
FractureBrittle
TenacityBrittle
Mohs scale hardness2
|re|er}}Waxy, greasy, dull, earthy
DiaphaneityTransculent
Specific gravity4.88
Optical propertiesBiaxial (−)
Refractive indexnα = 1.720 nβ = 1.798 nγ = 1.805
Birefringence0.085
PleochroismStrong
2V angleMeasured 35°, calculated 32°
Dispersionr > v strong
Other characteristicsRadioactive.svg Radioactive
References[1][2][3]

Guilleminite (Ba(UO2)3(SeO3)2(OH)4·3H2O) is a uranium mineral named by R. Pierrot, J. Toussaint, and T. Verbeek in 1965 in honor of Jean Claude Guillemin (1923–1994), a chemist and mineralogist. It is a rare uranium/selenium mineral found at the Musonoi Mine in the Katanga Province of the Democratic Republic of the Congo.[2]

This secondary mineral also includes barium in its structure, in addition to selenium and uranium. It is bright yellow in colour and usually has an acicular crystal habit. It has a Mohs hardness of 2–3.[5]

Pleochroism

Guilleminite shows strong pleochroic attributes. Depending on the axis the gem is seen, guilleminite on the X axis can be seen in a bright yellow color, on the Y axis can be seen yellow, and on the Z axis is seen as a colorless gem.

References