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, so Thorutite leaves brownish, Brannerite leaves brownish-yellow; luster reads submetallic on Thorutite and vitreous on Brannerite.
How to tell apart: Streak differs, so Thorutite leaves brownish, Allanite leaves gray.
How to tell apart: Streak differs, so 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, 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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