Manandonite Locality: Sahatany Pegmatite Field (Mt Bity (Ibity) area), Manandona Valley, Vakinankaratra Region , Antananarivo Province , Madagascar ( Locality at mindat.org ) A UNIQUE and VERY UNCOMMON specimen of translucent, cream-colored, bladed botryoidal manandonite rosettes on matrix from the Sahatany Pegmatite Field of Madagascar. 4.3 x 3.5 x 2.0 cm — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Manandonite
Manandonite is an IMA-recognized mineral species in the silicate class, with the chemical formula Li₂Al₄(Si₂AlB)O₁₀(OH)₈.
It crystallizes in the triclinic crystal system (space group C1). It is a member of the Serpentine, Clay structural group.
Key properties: Mohs hardness 2.5; specific gravity 2.76–2.89; Pearly on cleavages luster; optically biaxial.
IMA symbol Mnd, grandfathered status — known before the IMA’s founding, named in 1912.
Found in miarolitic cavities developed in corroded differentiated quartz-microcline- tourmaline-bearing pegmatites.
It is found associated with Elbaite, quartz, microcline, albite.
The name refers to the Manandona River, nearby the type locality in Madagascar.