Class : Silicates
    Subclass : Phyllosilicates
    Crystal System : Monoclinic
    Chemistry : (Fe,Al)₃(Si,Al)₂O₅(OH)₄
    Rarity : Uncommon

Berthierine is a complex phyllosilicate close to chlorite and glauconite. It is a probably fairly common but unattractive weathering mineral that is often difficult to characterize with certainty. It was named in honor of the French chemist Pierre Berthier. Berthierine is found in various environments, particularly in marine sediments, in certain lateritic or polar soils, in coal deposits, and quite often in iron formations such as Hayange (Lorraine) or Knob Lake (Canada). Berthierine forms tiny flakes agglomerated into microcrystalline oolitic aggregates, of a dark olive green to dark yellowish green hue.

Main photo : Berthierine from Poudrette Quarry, Quebec, Canada © Alex Earl

No known twin for this mineral species.

No fake or treatments identified for this mineral species, but difficult to identify without heavy laboratory equipment.