Francevillite
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Francevillite is a uranyl-group vanadate mineral in the tyuyamunite series. Its chemical formula is (Ba,Pb)(UO2)2V2O8·5(H2O). Francevillite is a strongly radioactive mineral. It is typically orange, yellow or brownish yellow. It forms a series with curienite.[2]
Quick Facts General, Category ...
Francevillite | |
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General | |
Category | Vanadate mineral |
Formula (repeating unit) | (Ba,Pb)(UO2)2V2O8·5(H2O) |
IMA symbol | Fvl[1] |
Strunz classification | 4.HB.15 |
Dana classification | 40.02a.27.01 |
Crystal system | Orthorhombic |
Crystal class | Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) |
Space group | Pcan |
Unit cell | a = 10.41, b = 8.51 c = 16.76 [Å]; Z = 4 |
Identification | |
Color | Lemon-yellow, yellow-orange, orange, greenish yellow; green, brown |
Crystal habit | Aggregates and incrustations of crystals, also massive, in veinlets and as impregnations |
Cleavage | On {001}, perfect |
Mohs scale hardness | 3 |
Luster | Adamantine - pearly |
Streak | Light yellow |
Diaphaneity | Semitransparent |
Specific gravity | 4.55 |
Optical properties | Biaxial (-) |
Refractive index | nα = 1.750 - 1.785 nβ = 1.910 - 1.952 nγ = 1.945 - 2.002 |
Birefringence | δ = 0.195 - 0.217 |
Pleochroism | X = colorless; Y = Z = yellow |
2V angle | Measured: 52°, Calculated: 46° to 52° |
Other characteristics | Radioactive |
References | [2][3][4][5] |
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