White crystals of the rare mineral parakeldyshite from Norway (Bratthagen Quarries, Lågendalen, Hedrum, Larvik, Vestfold, Norway). Parakeldyshite is a zirconium mineral. — Photo: David Hospital · CC BY-SA 4.0
Parakeldyshite
Parakeldyshite is an IMA-recognized mineral species in the silicate class, with the chemical formula Na₂ZrSi₂O₇.
It crystallizes in the triclinic crystal system (space group P-1).
Key properties: Mohs hardness 5.5–6; specific gravity 3.37–3.39; Vitreous luster; optically biaxial.
IMA symbol Pkel, IMA status: approved, named in 1975.
Occurs as masses in nepheline syenite pegmatites which cut a foyaite (Bratthagen, Norway).
It is found associated with Alkalic feldspar, nepheline, aegirine, pyrophanite, loparite, biotite (Bratthagen, Norway); sodalite, analcime, tetranatrolite, aegirine.
Its name comes from the Greek para, for near, and its relation to keldyshite.