Kimuraite-(Y)

minerals

lanthanite

lokkaite

kozoite

Formula: CaY2(CO3)4.6H2O
Hydrated normal carbonate, tengerite group
Specific gravity: 2.6
Hardness: 2½
Streak: White
Colour: Pale purple, light pink, white
Solubility: Soluble in hydrochloric acid with effervescence (Dana)
Environments

Hydrothermal environments

Kimuraite is a secondary carbonate found in fissures in alkali olivine basalt (Webmin, HOM), associated with lanthanite-(Nd), lanthanite-(La), lokkaite-(Y) and kozoite-(Nd) (HOM).

Localities

At the type locality, Kirigo, Hizen-cho, Karatsu City, Saga, Japan, kimuraite occurs in fissues in alkali olivine basalt (Mindat, Dana, AM 71.1028-1033), associated with lokkaite-(Y) and lanthanite-(Nd). The exposures of kimuraite-bearing basalt are distributed over 5 km around the first locality.The basalt has a homogeneous groundmass with olivine phenocrysts to 2 mm across. The rare-earth-element carbonates are exclusively found in minor fissures developed nearly parallel to the flow structure. Kimuraite is closely associated with coarser-grained lanthanite. These two minerals are in most cases underlain by lokkaite, which forms aggregates on fissure walls (AM 71, 1028-1033).

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