:Locality: Vasin-Myl'k Mountain, Kola, Russian Federation Size: 2.8 × 1.7 × 0.5 cm Description: Polished chip of a granitoid containing Rb rich microcline and rubicline. Rubicline is the Rb analogue of microcline, (Rb,K)AlSi3O8, ideally RbAlSi3O8, and occurs in granitic pegmatites. Accompanied by pollucite, 'mica' and quartz. Only 4 accepted species contains Rb, and rubicline was the first mineral described with rubidium as an essential constituent. IMA1996-058. — Photo: Joan Rosell , from rosellminerals.com · CC BY-SA 4.0
Rubicline
The rubidium analogue of microcline — a rare Rb-feldspar found in highly evolved lithium pegmatites.
Intro adapted from Wikipedia (CC BY-SA).
Rubicline is an IMA-recognized mineral species in the silicate class, with the chemical formula Rb(AlSi₃O₈).
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Feldspar structural group.
Key properties: [White.] streak; [Vitreous.] luster; refractive index 1.524; optically biaxial.
IMA symbol Rub, IMA status: approved, named in 1996.
Found in the core zones of complex Li-Cs-Rb-enriched, rare-element, granitic pegmatites, by exsolution from a K-Na-Rb-enriched precursor, followed possibly by fluid-induced modification.
It is found associated with Rubidian microcline, albite, muscovite, quartz, apatite, pollucite.
Indicates the rubidium analogue of microcline.