Thorbastnäsite is a rare thorium-dominant member of the bastnäsite group, typically found as tiny, brownish to yellow platy crystals. It is primarily sought after by specialized rare-earth element collectors due to its radioactive nature and association with unique pegmatite and skarn environments.

Hardness

4-4.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrareBastnäsite Group family

Thorbastnäsite

Hardness: 4-4.5
Luster: Vitreous
Streak: White
Transparency: Translucent

Is this thorbastnäsite?

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 thorbastnäsite with a known reference. Thorbastnäsite sits at Mohs 4-4.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Thorbastnäsite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Thorbastnäsite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: yellow, brown, colorless.
5
Look at form & habit
Crystal system: hexagonal. Typical habit: platy crystals, granular aggregates.

Often found alongside thorbastnäsite

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

All properties

Chemical formula: (Th,Ca)(CO₃)F₂
Mohs hardness: 4-4.5
Density: 5.0-5.2 g/cm³
Colors: Yellow Brown Colorless
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Hexagonal
Crystal habit: Platy Crystals, Granular Aggregates
Cleavage: Distinct
Rarity: Rare
Uses: Collector
Host rock: Skarn Deposits, Rare-earth Element Pegmatites
Typical price: $50-300 per thumbnail specimen

Where rockhounds find thorbastnäsite

Classic worldwide localities

Bastnäs, Sweden
Kola Peninsula, Russia
Bayankhongor Province, Mongolia

Field-hunting tip

Look in skarn deposits, rare-earth element pegmatites country — that is the host setting where thorbastnäsite typically forms. If you start seeing allanite, cerite, fluorite in float, you are in the right ground. Field specimens usually show a platy crystals, granular aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify thorbastnäsite?+

Mohs hardness is 4-4.5. It typically shows a vitreous luster. The streak is white. Common colors include yellow, brown, colorless.

Where is thorbastnäsite found?+

Notable localities include Bastnäs, Sweden; Kola Peninsula, Russia; Bayankhongor Province, Mongolia.

How much is thorbastnäsite worth?+

Typical asking prices fall in the range of $50-300 per thumbnail specimen. Quality, size, and provenance can move individual specimens well outside that range.

Is thorbastnäsite safe to handle?+

This mineral is radioactive. Contains thorium, which is radioactive. Handle with care, avoid creating dust, and wash hands thoroughly after contact; store away from other sensitive minerals and living spaces. Handle with care, avoid grinding or breathing dust, and store separately.

What minerals are found with thorbastnäsite?+

Thorbastnäsite commonly co-occurs with Allanite, Cerite, Fluorite, Quartz. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does thorbastnäsite form in?+

Thorbastnäsite typically forms in skarn deposits, rare-earth element pegmatites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is thorbastnäsite used for?+

Thorbastnäsite is used in collector.

Find thorbastnäsite on the map

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