Leonardsenite
Leonardsenite is an IMA-recognized mineral species in the halide class, with the chemical formula MgAlF₅·2H₂O.
It crystallizes in the orthorhombic crystal system (space group Imma). It is a member of the Weberite structural group.
Key properties: specific gravity 2.31; White streak; Earthy (aggregates) luster.
IMA symbol Lnd, IMA status: approved, named in 2011.
A sublimated encrustations from fluorine-rich fumarolic gas.
It is found associated with Jakobssonite, anhydrite, ralstonite, jarosite, anhydrous AlF3, opal-A, oskarssonite (Heimaey); ralstonite, opal-A, jakobssonite, malladrite, fluorite (Heckla).
The mineral was named to honor Erik Leonardsen (b. 1934), the former leader of the X-ray Diffraction Laboratory of the Geological Institute, University of Copenhagen, Denmark.