Iimoriite-(Y)

Chemical formula: Y₂(SiO₄)(CO₃)

Iimoriite-(Y) is a rare yttrium carbonate-silicate, forming brown, resinous masses and poorly formed crystals in pegmatites.

## Characteristics Iimoriite-(Y) is a mineral belonging to the carbonate-silicate group, containing yttrium. It typically occurs as irregular, resinous masses or aggregates of poorly formed, tabular crystals, which rarely exceed a few millimeters. Its appearance is inconspicuous, and specimens are most often yellowish-brown to reddish-brown. This mineral is brittle and opaque or only translucent on thin edges. ## Physical Properties It is characterized by a Mohs hardness of approximately 6. It has a vitreous to resinous luster. The density of the mineral is quite high, around 4.14 g/cm³, which is typical for minerals rich in rare earth elements, such as yttrium. ## Colors and Varieties Iimoriite-(Y) occurs in shades of brown – from yellowish-brown, through reddish-brown, to dark brown. No color or commercial varieties are distinguished. ## History and Name The mineral was discovered in Japan and described in 1967 by Akira Kato and Kozo Nagashima. Its name honors Japanese mineralogists, Dr. Satoyasu Iimori and his son, Dr. Takeo Iimori, for their contributions to research on rare earth minerals. The suffix "-(Y)" in the name indicates the dominant rare earth element in its composition, which is yttrium. ## Applications Iimoriite-(Y) has no industrial applications. Its significance is purely scientific and as a collector's item, being a rare mineral containing rare earth elements.

Properties

Mohs hardness
5.5-6
Color
Buff-tan, light purplish gray
Luster
Resinous to vitreous
Streak
White with purplish gray-tint
Density
4.47
Cleavage
distinct on (011)
Fracture
Uneven
Transparency
Transparent
Crystal system
Triclinic

Diagnostic features

## Identification Iimoriite-(Y) can be identified by its characteristic resinous luster, brown color, high density, and occurrence in granitic pegmatites. It often forms massive, amorphous aggregates rather than well-formed crystals. It reacts with acids, which is a diagnostic feature for carbonates. ## Distinguishing from Similar Minerals It can be confused with other brown pegmatite minerals, such as gadolinite, euxenite, or allanite. Differentiation requires advanced research methods, such as chemical analysis (EDS) to confirm the presence of silicon, carbon, and yttrium. In field conditions, it is practically impossible to identify unambiguously. ## Crystal Forms Crystals are very rare, poorly formed, and have a tabular or short prismatic habit. Typically, iimoriite-(Y) occurs as granular aggregates or irregular masses embedded in the host rock.

Geological environment

## Genesis Iimoriite-(Y) is a mineral of magmatic origin, crystallizing in the late stages of the evolution of granitic pegmatites, rich in rare earth elements. ## Mineral Associations It most often co-occurs with quartz, microcline, albite, biotite, as well as with other rare earth minerals such as gadolinite-(Y), tengerite-(Y), thalenite-(Y), fergusonite-(Y), and allanite-(Ce). ## Localities The most important and classic locality, from which the best-studied specimens originate, is the Bø pegmatite in the Tørdal region, Norway. The mineral was also found at its type locality in the Fusamata pegmatite in Fukushima Prefecture, Japan, as well as in Sweden (Östanmossa mine) and Italy (Baveno).

Rarity

Very rare

For collectors

## Quality Criteria The most valuable specimens for collectors are those with visible, even if small and poorly formed, crystals. Rich aggregates of the mineral in a contrasting rock matrix are also prized, especially in association with other rare minerals. Due to its general rarity, any analytically confirmed iimoriite-(Y) specimen has high scientific and collector value. ## Popular Localities The best specimens in the world are considered to come from the Bø pegmatite in Tørdal, Norway. They provide the richest aggregates and best-formed crystals of this mineral.

Care and storage

## Cleaning Specimens should be cleaned only mechanically, using a soft, dry brush or compressed air to remove dust. Due to its rarity and potential reactivity, contact with water and chemical agents should be avoided. ## What to Avoid Contact with acids, which can react with the carbonate part of its structure, should be avoided. The mineral is brittle, so it must be protected from impacts and falls. It should not be heated or subjected to ultrasound. ## Storage Iimoriite-(Y) specimens are best stored under stable conditions, in a sealed display box, away from dust, moisture, and direct sunlight. It is advisable to isolate it from other minerals to prevent scratches.

External references

Sources

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