12g watermelon tourmaline from Brazil — Photo: Jeremiasjeremias · CC BY 4.0
Rossmanite
A lithium-aluminium tourmaline with a partly vacant X site — pale-pink prisms in lithium pegmatites.
Intro adapted from Wikipedia (CC BY-SA).
Rossmanite is an IMA-recognized mineral species in the silicate class, with the chemical formula (Al₂Li)Al₆(Si₆O₁₈)(BO₃)₃(OH)₃(OH).
It crystallizes in the hexagonal crystal system (space group R3m). It is a member of the Tourmaline structural group.
Key properties: Mohs hardness 7.5; specific gravity 3; typically pink; White streak; Vitreous luster; optically uniaxial.
IMA symbol Rsm, IMA status: approved, named in 1996.
Found in lepidolite-subtype zoned pegmatite.
It is found associated with Lepidolite, albite, elbaite, apatite, topaz, beryl, amblygonite-montebrasite, manganocolumbite, cassiterite.
The mineral was named to honor George R. Rossman (b. 1945), California Institute of Technology, Pasadena, California.
Collections: Collector Favorites, Rare & Remarkable.