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Silicate

Gjerdingenite-Ca

K₂Ca(Nb,Ti)₄(Si₄O₁₂)₂(O,OH)₄·6H₂O
Hardness5
Crystal systemMonoclinic
ClassSilicate
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Gjerdingenite-Ca

Gjerdingenite-Ca is an IMA-recognized mineral species in the silicate class, with the chemical formula K₂Ca(Nb,Ti)₄(Si₄O₁₂)₂(O,OH)₄·6H₂O.

It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Labuntsovite structural group.

Key properties: Mohs hardness 5; specific gravity 2.79; White streak; Vitreous luster; optically biaxial.

IMA symbol Gje-Ca, IMA status: approved, named in 2005.

Occurs as alteration of vuonnemite formed in hydrothermal assemblages of peralkaline pegmatites related to agpaitic feldspathoidal syenites.

It is found associated with Microcline, natrolite, aegirine, organovaite-Mn, organovaite-Zn, beryllite, epididymite, altered steenstrupine-(Ce), ranciéite (pseudomorph after sérandite).

Signifies the structural analog of gjerdingenite-Mn with dominant Ca in the D structural site.

Index entry. This entry combines official IMA/RRUFF species data with published physical-property data — a full written entry hasn’t been published yet. Browse more G minerals or help write this entry.