Koninckite
Koninckite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Fe³⁺(PO₄)·3H₂O.
It crystallizes in the tetragonal crystal system.
Key properties: Mohs hardness 3.5; specific gravity 2.4; Pale yellow streak; Vitreous luster; optically uniaxial.
IMA symbol Kon, grandfathered status — known before the IMA’s founding, named in 1884.
Presumably as a secondary mineral in phosphatic sedimentary rocks (Richelle, Belgium); in a hydrothermally altered andesite enriched in Fe, SO4, and PO4 (Suwa mine, Japan).
It is found associated with Richellite, halloysite, allophane (Richelle, Belgium); tinticite, strengite, jarosite, goethite (Suwa mine, Japan).
The mineral was named to honor Laurent Guillaume de Koninck (1809–1887), Belgian geologist, University of Liège, Liège, Belgium.