Class : Silicates
    Subclass : Nesosilicates
    Crystal system : Monoclinic
    Chemistry : Fe₂Al₄Si₂O₁₀(OH)₄
    Rarity : Rare

Chloritoid is a silicate typical of rocks of low to medium gradient regional metamorphism (schists, chlorite mica-schists, garnet, muscovite, staurolite, etc...). Less commonly it is found in contact metamorphism, as a product of hydrothermal alteration of lavas, and in certain hydrothermal veins with quartz and carbonates. Its name comes from the Greek khlôros (green) and eidos (appearance) because of its resemblance to chlorites. The chloritoid appears essentially in lamellae with a hexagonal outline, united in lamellar to scaly aggregates, clearly coarser and more brittle than the lamellae of micas : clear, tabular crystals are rare. The chloritoid is dark green to greenish black in color.

Main photo : Chloritoid from Dara-e-Pech, Kunar, Afghanistan © Rob Lavinsky

Numerous twins are known around the axes [100], [110] and [130] and polysynthetics on {001}.

No fake identified for this mineral species.