Miyawakiite-(Y)

miyawakiite-(Y)

allanite-(Y)

britholite-(Y)

caysichite-(Y)

Images

Formula: ☐Y₄Fe₂(Si₈O₂₀)(CO₃)₄(H₂O)₃
Phyllosilicate (sheet silicate)
Crystal system: Tetragonal
Specific gravity: 2.95 calculated
Hardness: 3 to 4
Streak: White
Colour: Pale yellow
Environments

Pegmatites

Miyawakiite-(Y) is a new mineral, approved in 2024 and pending publication as of May 2025.

Localities

At the type locality, the Suishoyama pegmatite, Iizaka Village, Kawamata, Date District, Fukushima Prefecture, Japan, miyawakiite-(Y) was described from the abandoned granitic pegmatite mine. It is found as pale yellow thin plates and columnar crystals up to 0.8 mm in size, in gaps and crevices of allanite-(Y) and britholite-(Y), and further associated with caysichite-(Y), having formed after their alteration by near-surface waters (AM 110.5.831, Mindat).

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