Specimens of biotite mica from Madagascar. Biotite mica is a black, platy mineral which forms in sheets, it belongs to the mica group of minerals which also includes muscovite, phlogopite and lepidolite micas. Being a common phyllosilicate mineral, it is also found in many rocks, particularly of igneous and metamorphic origin, such as mica schist, gneisses and granites. The crystal system of mica in general is monoclinic and like other mica minerals, biotite has a perfect basal cleavage and consists of flexible sheets or lamellae, which easily flake off, with tabular to prismatic crystals. These samples of biotite mica are of a higher quality than our specimens from Pakistan and Norway, they are supplied in a white card tray with an information label.