Fluorluanshiweiite

fluorluanshiweiite

luanshiweiite

polylithionite

cookeite

Images

Formula: KLiAl1.50.5(Si3.5Al0.5)O10F2
Phyllosilicate (sheet silicate), mica group
Crystal System: Monoclinic
Specific gravity: 2.94 measured, 2.898 calculated
Hardness: ~3
Streak: Colourless, white
Colour: Silvery white
Environments

Pegmatites

Fluorluanshiweiite is a relatively new mineral, approved in 2019 and to date (June 2025) reported only from the type locality.

Localities

At the type locality, the Nanyangshan 703 deposit, Nanyangshan pegmatite field, Lushi County, Sanmenxia, Henan, China, the rare metal mineralisation is hosted in an lithium - cesium - tantalum (LCT) granitic pegmatite formed in the late stage of the evolution of the pegmatite-forming magmatic liquid.
Fluorluanshiweiite is closely associated with luanshiweiite, polylithionite, cookeite, albite, quartz and an unknown cesium-rich mica, and it is commonly found with spodumene, montebrasite, elbaite, fluorapatite, pollucite and nanpingite. Tantalite-(Mn), columbite-(Mn), bismutotantalite, stibiotantalite, oxynatromicrolite and fluornatromicrolite are some other associated minerals.
Fluorluanshiweiite occurs mostly in cookeite as a flaky residue, replaced by cesium-rich mica, or in the form of scale aggregates. Most individual grains are less than 1 mm in size, with the largest being ~1 cm, and the periphery is replaced by cookeite. Fluorluanshiweiite is silvery white as a hand specimen and greyish-white to colourless in a thin section, transparent with a white streak; it has a vitreous lustre and appears pearly on cleavage planes (Minerals, 10 (2) 93 doi:10.3390/min10020093).

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