francevillite

{{infobox mineral |boxbgcolor=#dacc1c| name = Francevillite | category = Vanadate mineral | image = Francevillite-Mounanaite-Curienite-20877.jpg | imagesize = 260px | alt = | caption = Yellow crystals of francevillite on matrix with small mounanaite crystals (specimen size, 4 x 3.5 x 1 cm) | formula = | IMAsymbol = Fvl | molweight = | strunz = 4.HB.15 | dana = 40.02a.27.01 | system = Orthorhombic | class = Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) | symmetry = Pcan | unit cell = a = 10.41, b = 8.51 c = 16.76 [Å]; Z = 4 | color = Lemon-yellow, yellow-orange, orange, greenish yellow; green, brown | colour = | habit = Aggregates and incrustations of crystals, also massive, in veinlets and as impregnations | twinning = | cleavage = On {001}, perfect | fracture = | tenacity = | mohs = 3 | luster = Adamantine - pearly | streak = Light yellow | diaphaneity = Semitransparent | gravity = 4.55 | density = | polish = | opticalprop = Biaxial (-) | refractive = 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 = Measured: 52°, Calculated: 46° to 52° | dispersion = | extinction = | length fast/slow = | fluorescence= | absorption = | melt = | fusibility = | diagnostic = | solubility = | other = 25px Radioactive | alteration = | references = }}

Francevillite is a uranyl-group vanadate mineral in the tyuyamunite series. Its chemical formula is . Francevillite is a strongly radioactive mineral. It is typically orange, yellow or brownish yellow. It forms a series with curienite.