Roscoelite is a green mineral from the mica group that contains vanadium.
The chemical formula is K , Mg 10(OH 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 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.