Brunogeierite is an extremely rare germanium-bearing mineral belonging to the spinel group. It is primarily found as microscopic octahedral crystals associated with lead-zinc ores at the Tsumeb mine in Namibia.
Is this brunogeierite?
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 brunogeierite with a known reference. Brunogeierite 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. Brunogeierite leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Brunogeierite typically shows a submetallic luster.
- 4Match the color rangeCompare against the expected color range: black.
- 5Look at form & habitCrystal system: cubic. Typical habit: octahedral crystals.
Often confused with
Brunogeierite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Luster reads submetallic on Brunogeierite and metallic on Magnetite.
How to tell apart: Streak differs — Brunogeierite leaves black, Franklinite leaves reddish-brown; luster reads submetallic on Brunogeierite and metallic on Franklinite.
Often found alongside brunogeierite
Minerals reported to co-occur with brunogeierite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Ge,Fe,Zn)Fe₂O₄
- Mohs hardness
- 5-6
- Density
- 5.32 g/cm³
- Colors
- Streak
- Black
- Luster
- Submetallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Octahedral Crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Mineral Deposits
- Typical price
- $200-1000+ for rare micro-specimens
Where rockhounds find brunogeierite
Classic worldwide localities
- Tsumeb Mine, Namibia
Field-hunting tip
Look in hydrothermal mineral deposits country — that is the host setting where brunogeierite typically forms. If you start seeing tennantite, galena, sphalerite in float, you are in the right ground. Field specimens usually show a octahedral crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find brunogeierite on the map
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