Tanteuxenite-(Y) is a rare radioactive member of the euxenite group characterized by its dominant tantalum content. It typically occurs as black to dark brown prismatic crystals or massive inclusions within complex granite pegmatites.

Hardness

5.5

Mohs

Luster

Submetallic

Streak

Yellowish-brown

Transparency

Opaque

mineralrareEuxenite Group family

Tanteuxenite-(Y)

Hardness: 5.5
Luster: Submetallic
Streak: Yellowish-brown
Transparency: Opaque

Is this tanteuxenite-(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 tanteuxenite-(y) with a known reference. Tanteuxenite-(Y) sits at Mohs 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. Tanteuxenite-(Y) leaves a yellowish-brown streak.
3
Read the luster
Hold the specimen under a strong light. Tanteuxenite-(Y) typically shows a submetallic luster.
4
Match the color range
Compare against the expected color range: black, brownish-black.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: prismatic crystals, massive, granular.

Often confused with

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

How to tell apart: Streak differs — Tanteuxenite-(Y) leaves yellowish-brown, Samarskite-(Y) leaves dark brown.

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Often found alongside tanteuxenite-(y)

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

All properties

Chemical formula: (Y,Ca,Ce,Th)(Ta,Nb,Ti)₂O₆
Mohs hardness: 5.5
Density: 5.8-6.1 g/cm³
Colors: Black Brownish-black
Streak: Yellowish-brown
Luster: Submetallic
Transparency: Opaque
Crystal system: Orthorhombic
Crystal habit: Prismatic Crystals, Massive, Granular
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Granite Pegmatites
Typical price: $50-300 per specimen

Where rockhounds find tanteuxenite-(y)

Classic worldwide localities

Hitra, Norway
Karelia, Russia
Iveland, Norway
Madagascar

Field-hunting tip

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

Common questions

How do you identify tanteuxenite-(y)?+

Mohs hardness is 5.5. It typically shows a submetallic luster. The streak is yellowish-brown. Common colors include black, brownish-black.

Where is tanteuxenite-(y) found?+

Notable localities include Hitra, Norway; Karelia, Russia; Iveland, Norway; Madagascar.

How much is tanteuxenite-(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 tanteuxenite-(y) safe to handle?+

This mineral is radioactive. Contains radioactive elements (thorium, yttrium) and frequently rare earth elements; handle with care and store in a lead-lined container or away from other specimens. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like tanteuxenite-(y)?+

Tanteuxenite-(Y) is most often confused with Euxenite-(Y), Samarskite-(Y). A quick hardness test and a streak check separate the look-alikes faster than color alone.

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

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

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

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

What is tanteuxenite-(y) used for?+

Tanteuxenite-(Y) is used in collector.

Find tanteuxenite-(y) on the map

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