Orthobrannerite is a rare uranium-bearing mineral often found as dark, prismatic crystals in pegmatite environments. Due to its high radioactivity and rarity, it is sought after specifically by advanced mineral collectors of uranium species.
Is this orthobrannerite?
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 orthobrannerite with a known reference. Orthobrannerite sits at Mohs 5.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: dark brown to black.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine.
- 4Match the color rangeCompare against the expected color range: black, brownish green.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: prismatic crystals.
Often confused with
Orthobrannerite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads adamantine on Orthobrannerite and pitchlike to vitreous when fresh, resinous to dull when altered on Brannerite.
How to tell apart: Streak differs, so Orthobrannerite leaves dark brown to black, Rutile leaves pale brown, yellowish brown; gray, greenish black with high nb–ta.
How to tell apart: Streak differs, so Orthobrannerite leaves dark brown to black, Ilmenite leaves black to reddish brown; luster reads adamantine on Orthobrannerite and metallic to submetallic on Ilmenite.
Often found alongside orthobrannerite
Minerals reported to co-occur with orthobrannerite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- UUTi₄O₁₂(OH)₂
- Mohs hardness
- 5.5
- Density
- 5.46 g/cm³
- Colors
- Streak
- Dark brown to black
- Luster
- Adamantine
- Transparency
- Semitransparent
- Crystal system
- Orthorhombic
- Crystal habit
- Prismatic crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In weathered biotite pyroxene syenite (Yunan, China); in an alkalic lamprophyre (Szechwan, China)
Where rockhounds find orthobrannerite
Classic worldwide localities
- Undefined localities in Yunan and Szechwan Provinces, China (type locality)
Field-hunting tip
Where it forms: In weathered biotite pyroxene syenite (Yunan, China); in an alkalic lamprophyre (Szechwan, China). If you start seeing quartz, albite, muscovite in float, you are in the right ground. Typical habit: prismatic crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify orthobrannerite?+
Where is orthobrannerite found?+
Is orthobrannerite safe to handle?+
What rocks look like orthobrannerite?+
What minerals are found with orthobrannerite?+
What kind of rock does orthobrannerite form in?+
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Find orthobrannerite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
