Yttrotantalite-(Y) is a rare yttrium-tantalum-niobium oxide mineral often found as dark, brownish-black prismatic crystals in pegmatites. It is notable for its heavy density and characteristic radioactive nature, requiring careful handling by collectors. It is typically sought after by mineralogists interested in rare-earth element bearing species.

Hardness

5-5.5

Mohs

Luster

Submetallic to vitreous, greasy

Streak

Gray

Transparency

Opaque, transparent in thin fragments

mineralrareSamarskite Group family

Yttrotantalite-(Y)

Hardness: 5-5.5
Luster: Submetallic to vitreous, greasy
Streak: Gray
Transparency: Opaque, transparent in thin fragments

Is this yttrotantalite-(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 yttrotantalite-(y) with a known reference. Yttrotantalite-(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. Streak: gray.
3
Read the luster
Hold the specimen under a strong light. Luster: submetallic to vitreous, greasy.
4
Match the color range
Compare against the expected color range: brownish black, yellowish brown, yellow.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: metamict, prismatic.

Often confused with

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

mineral

Columbite

Mohs 6

How to tell apart: Streak differs, so Yttrotantalite-(Y) leaves gray, Columbite leaves blackish brown.

Compare →

Often found alongside yttrotantalite-(y)

Minerals reported to co-occur with yttrotantalite-(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)(Ta,Nb)₂(O,OH)₄
Mohs hardness: 5-5.5
Density: 5.7 g/cm³
Colors: Brownish black Yellowish brown Yellow
Streak: Gray
Luster: Submetallic to vitreous, greasy
Transparency: Opaque, transparent in thin fragments
Crystal system: Orthorhombic
Crystal habit: Metamict, prismatic
Cleavage: {010}, indistinct
Rarity: Rare
Uses: Collector
Host rock: A rare accessory mineral in granite pegmatites

Where rockhounds find yttrotantalite-(y)

Classic worldwide localities

Rare Metals mine, Aquarius Mountains, Mohave Co., Arizona, USA
Ytterby, on Resarö Island, near Vaxholm, near Falun, at Finbo and Broddbo, Sweden
Skuleboda pegmatite, near Väne Ryr, Västergötland, Sweden
Hattevik, east of Dillingö, and near Berg, Norway
Tanokamiyama district, Shiga Prefecture, Japan

Field-hunting tip

Where it forms: A rare accessory mineral in granite pegmatites. If you start seeing albite, garnet, topaz in float, you are in the right ground. Typical habit: metamict, prismatic. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify yttrotantalite-(y)?+

Mohs hardness is 5-5.5. Luster: submetallic to vitreous, greasy. The streak is gray. Common colors include brownish black, yellowish brown, yellow.

Where is yttrotantalite-(y) found?+

Notable localities include Rare Metals mine, Aquarius Mountains, Mohave Co., Arizona, USA; Ytterby, on Resarö Island, near Vaxholm, near Falun, at Finbo and Broddbo, Sweden; Skuleboda pegmatite, near Väne Ryr, Västergötland, Sweden; Hattevik, east of Dillingö, and near Berg, Norway; Tanokamiyama district, Shiga Prefecture, Japan.

Is yttrotantalite-(y) safe to handle?+

Yttrotantalite-(Y) contains uranium or thorium and calls for real care. Contains radioactive elements (uranium and thorium) and should be stored with adequate shielding and kept away from prolonged skin contact or inhalation of dust.

What rocks look like yttrotantalite-(y)?+

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

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

Yttrotantalite-(Y) commonly co-occurs with Albite, Garnet, Topaz, Fergusonite, Monazite, Columbite. Spotting any of these in float or country rock is a useful trip signal.

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

Where it forms: A rare accessory mineral in granite pegmatites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is yttrotantalite-(y) used for?+

Yttrotantalite-(Y) is used in collector.

Find yttrotantalite-(y) on the map

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