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 pale brown streak.
- 3Read the lusterHold the specimen under a strong light. Thorutite typically shows a resinous 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 pale brown, Brannerite leaves brownish-yellow; luster reads resinous on Thorutite and vitreous 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-brown; luster reads resinous on Thorutite and submetallic 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
- (Th,U,Ca)Ti₂O₆
- Mohs hardness
- 5-6
- Density
- 6.0-6.4 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
- Granite Pegmatites
Where rockhounds find thorutite
Classic worldwide localities
- Kutyur-Tyube thorium deposit, near Urusai Peak, Sokh River basin, Alai Range, Kyrgyzstan
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
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.
