Iwashiroite-(Y) is an extremely rare yttrium tantalate mineral discovered in the granite pegmatites of Fukushima, Japan. Collectors typically find it as small, tabular brownish-black crystals associated with other rare earth minerals.

Hardness

4-5

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrare

Iwashiroite-(Y)

Hardness: 4-5
Luster: Vitreous
Streak: White
Transparency: Translucent

No image

Is this iwashiroite-(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 iwashiroite-(y) with a known reference. Iwashiroite-(Y) sits at Mohs 4-5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Iwashiroite-(Y) leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Iwashiroite-(Y) typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: yellowish brown, brown, black.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: tabular crystals.

Often found alongside iwashiroite-(y)

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

All properties

Chemical formula: YTaO₄
Mohs hardness: 4-5
Density: 5.6-5.8 g/cm³
Colors: Yellowish Brown Brown Black
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Tabular Crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Granite Pegmatites
Typical price: $50-300 per specimen

Where rockhounds find iwashiroite-(y)

Classic worldwide localities

Kawamata, Fukushima Prefecture, Japan

Field-hunting tip

Look in granite pegmatites country — that is the host setting where iwashiroite-(y) typically forms. If you start seeing microcline, quartz, beryl in float, you are in the right ground. Field specimens usually show a tabular crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify iwashiroite-(y)?+

Mohs hardness is 4-5. It typically shows a vitreous luster. The streak is white. Common colors include yellowish brown, brown, black.

Where is iwashiroite-(y) found?+

Notable localities include Kawamata, Fukushima Prefecture, Japan.

How much is iwashiroite-(y) worth?+

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

Is iwashiroite-(y) safe to handle?+

This mineral is radioactive. Contains minor elements that may be radioactive; handle with care and wash hands after handling. Handle with care, avoid grinding or breathing dust, and store separately.

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

Iwashiroite-(Y) commonly co-occurs with Microcline, Quartz, Beryl, Muscovite. Spotting any of these in float or country rock is a useful trip signal.

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

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

What is iwashiroite-(y) used for?+

Iwashiroite-(Y) is used in collector.

Find iwashiroite-(y) on the map

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