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. Thorutite leaves a brownish streak.
- 3Read the lusterHold the specimen under a strong light. Thorutite typically shows a submetallic luster.
- 4Match the color rangeCompare against the expected color range: black, brownish-black.
- 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 — Thorutite leaves brownish, Brannerite leaves brownish-yellow; luster reads submetallic on Thorutite and vitreous on Brannerite.
How to tell apart: Streak differs — Thorutite leaves brownish, Allanite leaves gray.
How to tell apart: Streak differs — Thorutite leaves brownish, Euxenite leaves yellowish, grayish, or reddish-brown; luster reads submetallic on Thorutite and submetallic, resinous, greasy on Euxenite.
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
- (Th,U,Ca)Ti₂O₆
- Mohs hardness
- 5-6
- Density
- 6.0-6.4 g/cm³
- Colors
- Streak
- Brownish
- Luster
- Submetallic
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic Crystals, Massive
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Granite Pegmatites
- Typical price
- $50-300 per specimen depending on size and quality
Where rockhounds find thorutite
Classic worldwide localities
- Kyzyl-Kum, Uzbekistan
- Suishoyama, Japan
- Brezhnevskoye, Russia
Field-hunting tip
Look in granite pegmatites country — that is the host setting where thorutite typically forms. If you start seeing quartz, feldspar, biotite in float, you are in the right ground. Field specimens usually show a prismatic crystals, massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find thorutite on the map
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