Thorutite is a rare thorium-dominant member of the brannerite group, typically found as heavy, dark, radioactive masses or small prismatic crystals. Collectors primarily seek it as a rare-earth mineral curiosity, usually occurring within granitic pegmatite environments.
Is this thorutite?
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 thorutite with a known reference. Thorutite 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. Streak: pale brown.
- 3Read the lusterHold the specimen under a strong light. Luster: resinous.
- 4Match the color rangeCompare against the expected color range: black, dark brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals, massive.
Often confused with
Thorutite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Thorutite leaves pale brown, Brannerite leaves dark greenish brown to yellowish brown; luster reads resinous on Thorutite and pitchlike to vitreous when fresh, resinous to dull when altered on Brannerite.
How to tell apart: Streak differs, so Thorutite leaves pale brown, Allanite leaves gray; luster reads resinous on Thorutite and submetallic on Allanite.
How to tell apart: Streak differs, so Thorutite leaves pale brown, Euxenite-(Y) leaves yellowish, grayish, or reddish brown; luster reads resinous on Thorutite and brilliant submetallic, waxy to resinous on fractures on Euxenite-(Y).
Often found alongside thorutite
Minerals reported to co-occur with thorutite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- ThTi₂O₆
- Mohs hardness
- 5-6
- Density
- 5.82 g/cm³
- Colors
- Streak
- Pale brown
- Luster
- Resinous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic crystals, massive
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In veins of microcline and sericitized nepheline, in a syenite massif
Where rockhounds find thorutite
Classic worldwide localities
- Kutyur-Tyube thorium deposit, near Urusai Peak, Sokh River basin, Alai Range, Kyrgyzstan
Field-hunting tip
Where it forms: In veins of microcline and sericitized nepheline, in a syenite massif. If you start seeing thorite, zircon, calcite in float, you are in the right ground. Typical habit: prismatic crystals, massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify thorutite?+
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Find thorutite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
