Carboirite is an extremely rare iron aluminum germanium hydroxide mineral primarily found in the complex sulfide ores of the Tsumeb Mine. It typically presents as small, dark, opaque tabular crystals associated with other rare germanium-bearing species. It is a highly sought-after prize for advanced mineral collectors specializing in rare sulfides and oxides.
Is this carboirite?
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 carboirite with a known reference. Carboirite 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. Streak: black.
- 3Read the lusterHold the specimen under a strong light. Luster: submetallic.
- 4Match the color rangeCompare against the expected color range: black, dark brown.
- 5Look at form & habitCrystal system: triclinic. Typical habit: tabular crystals, massive.
Often confused with
Carboirite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads submetallic on Carboirite and metallic to submetallic on Ilmenite.
How to tell apart: Streak differs, so Carboirite leaves black, Hematite leaves cherry-red or reddish brown; luster reads submetallic on Carboirite and metallic or submetallic to dull on Hematite.
Often found alongside carboirite
Minerals reported to co-occur with carboirite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- FeAl₂GeO₅(OH)₂
- Mohs hardness
- 5-6
- Colors
- Streak
- Black
- Luster
- Submetallic
- Transparency
- Opaque
- Crystal system
- Triclinic
- Crystal habit
- Tabular crystals, massive
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- hydrothermal polymetallic deposits
Where rockhounds find carboirite
Classic worldwide localities
- Tsumeb Mine, Namibia
Field-hunting tip
Where it forms: hydrothermal polymetallic deposits. If you start seeing germanite, renierite, tennantite in float, you are in the right ground. Typical habit: tabular crystals, massive. Train your eye for that shape before scanning the outcrop.
Common questions
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Find carboirite on the map
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