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.
Is this iwashiroite-(y)?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch iwashiroite-(y) with a known reference. Iwashiroite-(Y) sits at Mohs 6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pale brown.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to sub-adamantine.
- 4Match the color rangeCompare against the expected color range: amber brown, brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy, striated.
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
- 6
- Density
- 7.135 g/cm³
- Colors
- Amber brownBrown
- Streak
- Pale brown
- Luster
- Vitreous to sub-adamantine
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Platy, striated
- Cleavage
- Good on {010}; poor on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In an NYF-type granitic pegmatite
Where rockhounds find iwashiroite-(y)
Classic worldwide localities
- Suishoyama mine, Kawamata, Fukushima Prefecture, Japan
Field-hunting tip
Where it forms: In an NYF-type granitic pegmatite. If you start seeing quartz, microcline, annite in float, you are in the right ground. Typical habit: platy, striated. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify iwashiroite-(y)?+
Where is iwashiroite-(y) found?+
Is iwashiroite-(y) safe to handle?+
What minerals are found with iwashiroite-(y)?+
What kind of rock does iwashiroite-(y) form in?+
What is iwashiroite-(y) used for?+
Find iwashiroite-(y) on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
