Iimoriite-(Y) is a rare yttrium-bearing silicate-carbonate mineral first discovered in the Iimori mine in Japan. It typically occurs as massive, granular aggregates in granitic pegmatites and is often associated with other rare-earth minerals like xenotime and fergusonite.

Hardness

5-5.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrare

Iimoriite-(Y)

Hardness: 5-5.5
Luster: Vitreous
Streak: White
Transparency: Translucent

Is this iimoriite-(y)?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch iimoriite-(y) with a known reference. Iimoriite-(Y) sits at Mohs 5-5.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Iimoriite-(Y) leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Iimoriite-(Y) typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: white, gray, yellowish-white.
5
Look at form & habit
Crystal system: trigonal. Typical habit: granular, massive, rarely distinct crystals.

Often confused with

Iimoriite-(Y) vs. its common look-alikes — and how to tell them apart in the field.

Often found alongside iimoriite-(y)

Minerals reported to co-occur with iimoriite-(y). Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: Y₂(SiO₄)(CO₃)
Mohs hardness: 5-5.5
Density: 4.25-4.35 g/cm³
Colors: White Gray Yellowish-white
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Trigonal
Crystal habit: Granular, Massive, Rarely Distinct Crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Granite Pegmatites
Typical price: $50-300 per specimen depending on size and provenance

Where rockhounds find iimoriite-(y)

Classic worldwide localities

Iimori mine, Fukushima Prefecture, Japan
Kola Peninsula, Russia
Strange Lake, Quebec, Canada

Field-hunting tip

Look in granite pegmatites country — that is the host setting where iimoriite-(y) typically forms. If you start seeing xenotime, fergusonite, allanite in float, you are in the right ground. Field specimens usually show a granular, massive, rarely distinct crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify iimoriite-(y)?+

Mohs hardness is 5-5.5. It typically shows a vitreous luster. The streak is white. Common colors include white, gray, yellowish-white.

Where is iimoriite-(y) found?+

Notable localities include Iimori mine, Fukushima Prefecture, Japan; Kola Peninsula, Russia; Strange Lake, Quebec, Canada.

How much is iimoriite-(y) worth?+

Typical asking prices fall in the range of $50-300 per specimen depending on size and provenance. Quality, size, and provenance can move individual specimens well outside that range.

Is iimoriite-(y) safe to handle?+

This mineral is radioactive. Contains minor rare earth elements and thorium as trace impurities, requiring standard handling precautions for radioactive minerals. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like iimoriite-(y)?+

Iimoriite-(Y) is most often confused with Stillwellite-(Ce). A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with iimoriite-(y)?+

Iimoriite-(Y) commonly co-occurs with Xenotime, Fergusonite, Allanite, Quartz. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does iimoriite-(y) form in?+

Iimoriite-(Y) typically forms in granite pegmatites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is iimoriite-(y) used for?+

Iimoriite-(Y) is used in collector.

Find iimoriite-(y) on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.