Priscillagrewite-(Y)

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Formula: YCa₂Zr₂Al₃O₁₂
Oxide, garnet supergroup, yttrium- and zirconium- bearing mineral
Crystal System: Isometric
Specific gravity: 4.48 calculated
Hardness: 7 to 7½
Colour: Pale yellowish tinge
Environments

Sedimentary environments
Metamorphic environments

Priscillagrewite-(Y) is a new mineral, approved in 2020. It is an unusual member of the bitikleite group within the garnet supergroup, related to rubinite and eringaite, that are garnets thought to be some of the first solids to crystallise in the solar nebula R&M 97.5.461-463).

Localities

At the type locality, the Daba marble quarry, Daba, Daba-Siwaqa complex, Transjordan Plateau, Amman Governorate, Jordan, the formation consists of apatite layered marble from protoliths of bituminous marls, and limestone intercalated with phosphorite.
Priscillagrewite-(Y) occurs as diomorphic (having two different forms), isometric crystals up to 15 μm in size.
It is suggested that the source material for priscillagrewite-(Y) is not from rare-earth-element containing phosphatic minerals such as fluorapatite, but likely from detrital zircon as the source of both the zirconium and the yttrium (AM 107.318).
Priscillagrewite-(Y) occurs as tiny transparent, undistorted crystals with a pale yellow tint and vitreous lustre. The matrix is a green fluorapatite and spurrite layer coloured by vanadium that also includes irregular distributions of baghdadite, cuprite, ellinaite, fluormayenite, hematite, lakargiite, mcconnellite, perovskite (both yttrium-bearing and yttrium-free), sphalerite, tululite, vapnikite and zincite, as well as members of the andradite-grossular series, members of the brownmillerite-srebrodolskite series, members of the lime-monteponite series and members of the magnesiochromite-zincochromite series.
The rock layer in which priscillagrewite-(Y) was discovered was converted to marble by pyrometamorphism that may have reached 1,000°C. The pyrometamorphism appears to have resulted from the burning of plentiful hydrocarbons in the preexisting limestone R&M 97.5.461-463).

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