Cayalsite-(Y)

cayalsite-(Y)

bastnasite-(Ce)

vyuntspakhkite-(Y)

hundholmenite-(Y)

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Formula: CaY₆Al₂Si₄O₁₈F₆
Nesosilicate (insular SiO₄ groups), yttrium-bearing mineral
Crystal System: Orthorhombic
Specific gravity: 4.81 to 4.86 measured
Hardness: 6½
Colour: Colourless to faintly pink
Luminescence: No fluorescence under UV
Environments

Pegmatites

Cayalsite-(Y) is a relatively new mineral, approved in 2012 and to date (April 2023) reported only from the type localities

Localities

There are two co-type localities, the Øvre Lapplægeret Quarry, Lapplægeret, Drag, Hamarøy, and the Stetind pegmatite, Narvik, both in Nordland, Norway.
Cayalsite-(Y) occurs in several polytypic modifications arising from the combination of three non-equivalent structural layers. Predominantly heavy lanthanide elements substitute for Y and Ca, with some Ca also substituting for the rare-earth elements.
Cayalsite-(Y) forms colourless to faintly pink, prismatic crystals in cavities of yttrian fluorite in two granitic pegmatites (EJM 27.683-694).
Cayalsite-(Y) is a late-stage mineral in the granitic NYF (niobium, yttrium, fluorine) pegmatites. Associated minerals include bastnäsite-(Ce), hematite, vyuntspakhkite-(Y) and hundholmenite-(Y) (HOM).

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