roscoelite

{{Infobox mineral | name = Roscoelite | category = Phyllosilicate minerals | group = Mica group, dioctahedral mica group | boxwidth = | boxbgcolor = | image = Gold & roscoelite (Stuckslacker Mine, Coloma, California, USA) (16562912783).jpg | imagesize = 260px | caption = Roscoelite and gold | formula = K(V3+,Al,Mg)2AlSi3O10(OH)2 | IMAsymbol = Rcl | molweight = 426.53 g/mol | strunz = 9.EC.15 | system = Monoclinic | class = Prismatic (2/m) (same H-M symbol) | symmetry = C2/m | colour = olive-green to green-brown | habit = scales, fans, druses, rosettes, fibrous or felted aggregate. | twinning = | cleavage = Perfect plane {0,0,1} | fracture = platy | tenacity = | mohs = 1 | lustre = pearly | polish = | refractive = nα=1.60 nβ=1.66 nγ=1.67 | opticalprop = Biaxial (-) | birefringence = δ = | dispersion = | pleochroism = olive green to green-brown | fluorescence= | absorption = | streak = | gravity = 2.92 - 2.96 | density = | fusibility = loses water | diagnostic = | diaphaneity = semi-transparent to translucent | other = | references = }} Roscoelite is a green mineral from the mica group that contains vanadium. The chemical formula is K(V3+, Al, Mg)2AlSi3O10(OH)2. Crystals of roscoelite take on the monoclinic form, and are from the 2/m point group. The appearance is semi transparent to translucent coloured olive brown to green brown. The lustre is pearly. The mineral shows pleochroism with X showing green-brown, and Y and Z axes showing olive-green colour. The mineral was named after Henry Enfield Roscoe who first produced vanadium metal.

==Chemical properties== Roscoelite is a muscovite with aluminium substituted with vanadium. Vanadium can also be substituted by magnesium, iron, or manganese.