Colorless and beige acicular crystals of the very rare mineral potassic-jeanlouisite (IMA 2018-050) from the type and only known locality worldwide (Zirkel Mesa, Leucite Hills, Sweetwater County, Wyoming, United States of America). Ex. Erich Laskowski collection (USA). — Photo: David Hospital · CC BY 4.0
Potassic-jeanlouisite
Potassic-jeanlouisite is an IMA-recognized mineral species in the silicate class, with the chemical formula K(NaCa)(Mg₄Ti)Si₈O₂₂O₂.
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Amphibole structural group.
Key properties: specific gravity 3.146; White streak; Vitreous luster; optically biaxial.
IMA symbol Pjl, IMA status: approved, named in 2018.
Derived from potassic richterite via the coupled exchange CMg–1WOH––2CTi4+1WO2–2. In a specimen of leucite-lava.
It is found associated with Leucite, amphibole. Distribution From Zirkle Mesa, Leucite Hills, near Superior, Wyoming, USA.
The mineral was named to honor Jean-Louis Robert (1948-2017) for contributions to the crystal-chemical characterization of micas and amphiboles.