Tokkoite
Tokkoite is an IMA-recognized mineral species in the silicate class, with the chemical formula K₂Ca₄Si₇O₁₈(OH)F.
It crystallizes in the triclinic crystal system (space group P-1).
Key properties: Mohs hardness 4–5; specific gravity 2.761; Vitreous luster; optically biaxial.
IMA symbol Tok, IMA status: approved, named in 1985.
Found in nearly monomineralic segregations in an alkalic massif.
It is found associated with Charoite, tinaksite, miserite, aegirine, potassic feldspar.
The name refers to the Tokko River, nearby the type locality in Russia.
Index entry. This entry combines official IMA/RRUFF species data with published physical-property data — a full written entry hasn’t been published yet.
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