Thoreaulite is a very dense and rare tin tantalum oxide mineral primarily found in granitic pegmatites. Collectors often identify it by its high specific gravity, resinous luster, and characteristic tabular crystal habit often associated with other tin and tantalum-bearing minerals.
Is this thoreaulite?
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 thoreaulite with a known reference. Thoreaulite sits at Mohs 6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brown to yellow, slightly greenish.
- 3Read the lusterHold the specimen under a strong light. Luster: resinous to adamantine on the cleavage.
- 4Match the color rangeCompare against the expected color range: brown, yellowish, yellow brown, resin brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic.
Often confused with
Thoreaulite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside thoreaulite
Minerals reported to co-occur with thoreaulite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- SnTa₂O₆
- Mohs hardness
- 6
- Density
- 7.6-7.9 g/cm³
- Colors
- Streak
- Brown to yellow, slightly greenish
- Luster
- Resinous to adamantine on the cleavage
- Transparency
- Opaque, transparent in thin fragments
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic
- Cleavage
- {100}, perfect; {011}, imperfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A very rare mineral formed in differentiated granite pegmatites deficient in O, Fe, Mn, Na, Ca, and F
Where rockhounds find thoreaulite
Classic worldwide localities
- Congo (Zaire), from the Manono pegmatite, Katanga (Shaba) Province, and the Maniéma district, Kivu Province
- Gitebi, near Rutsiro, Rwanda
- Urubú pegmatite, Itinga, Minas Gerais, Brazil
- Ungursai, Kazakhstan
Field-hunting tip
Where it forms: A very rare mineral formed in differentiated granite pegmatites deficient in O, Fe, Mn, Na, Ca, and F. If you start seeing cassiterite, lithiotantite, microlite in float, you are in the right ground. Typical habit: prismatic. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify thoreaulite?+
Where is thoreaulite found?+
What rocks look like thoreaulite?+
What minerals are found with thoreaulite?+
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Find thoreaulite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
