A platy serpentine with an ideal composition of (Ni_1.75Al_1.0)(Si_1.5Al_0.5)O₅(OH)₄. Crystals are generally poorly crystalline mixtures of hexagonal and monoclinic polytypes. Poorly described, Al-rich material similar to a Ni analogue of amesite (referred to as “nimesite”) was redefined as brindleyite. Brindleyite is compositionally similar to berthierine because of the tetrahedral Si/Al ratio and structurally similar owing to the hexagonal and monoclinic polytype intergrowths. Brindleyite has been found in the Marmara bauxite deposit, Greece.
Cf., amesite, berthierine, garnierite, nepouite, pecoraite, pimelite, willemseite