Crystals of tiettaite from the TL and only known locality worldwide in Khibiny (Khibiny Massif, Murmansk Oblast, Russian Federation). Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Tiettaite
Tiettaite is an IMA-recognized mineral species in the silicate class, with the chemical formula K₄Na₁₂Fe³⁺₂Si₁₆O₄₁(OH)₄·2H₂O.
It crystallizes in the orthorhombic crystal system (space group Cmcm).
Key properties: Mohs hardness 3; specific gravity 2.42; [White.] streak; Vitreous or silky luster; optically biaxial.
IMA symbol Tie, IMA status: approved, named in 1991.
Found in unweathered ultra-alkalic pegmatites in an alkalic massif.
It is found associated with Nepheline, orthoclase, sodalite, aegirine, rasvumite, natrite, many others.
The name comes from the Saamsk word tietta, for science or knowledge, also after the name of the first Khibiny research laboratory founded by A.E. Fersman.