Kobeite-(Y) is a rare radioactive complex oxide mineral primarily found in granitic pegmatites. It typically occurs as small, dark prismatic crystals that often exhibit a brownish-black color and vitreous luster.
Is this kobeite-(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 kobeite-(y) with a known reference. Kobeite-(Y) sits at Mohs 5-6 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Kobeite-(Y) leaves a light yellowish brown streak.
- 3Read the lusterHold the specimen under a strong light. Kobeite-(Y) typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: black, brownish black.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: prismatic crystals, massive.
Often confused with
Kobeite-(Y) vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Kobeite-(Y) leaves light yellowish brown, Euxenite-(Y) leaves yellowish-brown; luster reads vitreous on Kobeite-(Y) and submetallic on Euxenite-(Y).
How to tell apart: Streak differs — Kobeite-(Y) leaves light yellowish brown, Samarskite-(Y) leaves dark brown; luster reads vitreous on Kobeite-(Y) and submetallic on Samarskite-(Y).
How to tell apart: Streak differs — Kobeite-(Y) leaves light yellowish brown, Fergusonite-(Y) leaves pale yellow.
Often found alongside kobeite-(y)
Minerals reported to co-occur with kobeite-(y). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Y,U,Fe)(Ti,Nb,Ta)₂O₆
- Mohs hardness
- 5-6
- Density
- 4.6-5.0 g/cm³
- Colors
- Streak
- Light Yellowish Brown
- Luster
- Vitreous
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Prismatic Crystals, Massive
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Granite Pegmatites
- Typical price
- $50-300 per specimen
Where rockhounds find kobeite-(y)
Classic worldwide localities
- Kobe, Japan
- Shiga Prefecture, Japan
- Fukushima Prefecture, Japan
Field-hunting tip
Look in granite pegmatites country — that is the host setting where kobeite-(y) typically forms. If you start seeing allanite, zircon, biotite in float, you are in the right ground. Field specimens usually show a prismatic crystals, massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify kobeite-(y)?+
Where is kobeite-(y) found?+
How much is kobeite-(y) worth?+
Is kobeite-(y) safe to handle?+
What rocks look like kobeite-(y)?+
What minerals are found with kobeite-(y)?+
What kind of rock does kobeite-(y) form in?+
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Find kobeite-(y) on the map
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