Bastnäsite-(La) is a rare-earth fluoride carbonate mineral primarily distinguished by its high Lanthanum content. It typically forms hexagonal tabular crystals or granular masses in alkaline igneous rocks and carbonatites, often appearing in brownish or yellowish hues.

Hardness

4-5

Mohs

Luster

Vitreous to greasy

Streak

White

Transparency

Translucent

mineralrareBastnäsite Group family

Bastnäsite-(La)

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

Is this bastnäsite-(la)?

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 bastnäsite-(la) with a known reference. Bastnäsite-(La) 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. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous to greasy.
4
Match the color range
Compare against the expected color range: yellow, reddish brown.
5
Look at form & habit
Crystal system: hexagonal. Typical habit: massive, prismatic.

Often confused with

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

How to tell apart: Streak differs, so Bastnäsite-(La) leaves white, Parisite-(Ce) leaves pale yellow.

All properties

Chemical formula: La(CO₃)F
Mohs hardness: 4-5
Density: 4.95-5 g/cm³
Colors: Yellow Reddish brown
Streak: White
Luster: Vitreous to greasy
Transparency: Translucent
Crystal system: Hexagonal
Crystal habit: Massive, prismatic
Cleavage: Imperfect on {1011}; indistinct on {0001}
Rarity: Rare
Uses: Collector, Ore of rare earth elements
Host rock: In late ankerite carbonatites (Belaya Zima deposit, Russia)

Where rockhounds find bastnäsite-(la)

Classic worldwide localities

Belaya Zima RE–Nb deposit, eastern Sayan, Siberia, Russia
Found near Odegi, Afu Hills, Nigeria

Field-hunting tip

Where it forms: In late ankerite carbonatites (Belaya Zima deposit, Russia). If you start seeing fluocerite, cerianite- in float, you are in the right ground. Typical habit: massive, prismatic. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify bastnäsite-(la)?+

Mohs hardness is 4-5. Luster: vitreous to greasy. The streak is white. Common colors include yellow, reddish brown.

Where is bastnäsite-(la) found?+

Notable localities include Belaya Zima RE–Nb deposit, eastern Sayan, Siberia, Russia; Found near Odegi, Afu Hills, Nigeria.

What rocks look like bastnäsite-(la)?+

Bastnäsite-(La) is most often confused with Bastnäsite-(Ce), Parisite-(Ce), Synchysite-(Ce). A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with bastnäsite-(la)?+

Bastnäsite-(La) commonly co-occurs with Fluocerite, Cerianite-. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does bastnäsite-(la) form in?+

Where it forms: In late ankerite carbonatites (Belaya Zima deposit, Russia). Working float back to the host body is the standard way to chase a fresh occurrence.

What is bastnäsite-(la) used for?+

Bastnäsite-(La) is used in collector, ore of rare earth elements.

Find bastnäsite-(la) on the map

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