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Formula: Na2NaBaCeZnSi6O17
Inosilicate (chain silicate), nordite supergroup
Specific gravity: 3.65 calculated
Colour: Pinkish

Hydrothermal environments

Illoqite-(Ce) is a new mineral, approved in 2021, and to date (March 2022) reported only from the type locality.


At the type locality, the Taseq Slope, Ilímaussaq complex, Kujalleq, Greenland, illoqite-(Ce) occurs in a hyperalkaline ussingite vein closely related to one of the largest ussingite veins in the Ilímaussaq complex. The associated minerals are aegirine, arfvedsonite, a britholite-group mineral, epistolite, chkalovite, lueshite, a manganese-rich pectolite group member and steenstrupine-(Ce). Illoqite-(Ce) crystallises as either single euhedral crystals up to 150 μm in size or radiating aggregates consisting of a few or many crystals. The aggregates are up to 200 μm in diameter. Illoqite-(Ce) can occur as scattered small groups of crystals or aggregates, but sometimes they occur in high concentrations creating clusters or bands almost completely consisting of illoqite-(Ce).
Alongside ussingite as a matrix mineral, aegirine and arfvedsonite occur as major components. Furthermore, the paragenesis of illoqite-(Ce) consists of britholite-(Ce), ancylite-(Ce), epistolite, chkalovite, lueshite, steenstrupine-(Ce) and polylithionite, where ancylite-(Ce) is the brownish weathering product of illoqite-(Ce) (MM 86.1.141-149).

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