Gengenbachite is a rare potassium iron phosphate. It was approved as a distinct mineral species in 2001, from material found at the Silberbrünnle mine, Haigerach valley near Gengenbach, central Black Forest, Germany.
Is this gengenbachite?
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 gengenbachite with a known reference. Gengenbachite sits at Mohs 2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: colorless, white.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: tabular crystals.
Often confused with
Gengenbachite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside gengenbachite
Minerals reported to co-occur with gengenbachite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KFe₃(H₂PO₄)₂(HPO₄)₄·6H₂O
- Mohs hardness
- 2
- Density
- 2.47 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Hexagonal
- Crystal habit
- Tabular crystals
- Cleavage
- Perfect basal
- Rarity
- Rare
- Uses
- Collector
- Host rock
- associated with organic-rich soils in protected cave environments
Where rockhounds find gengenbachite
Classic worldwide localities
- Grube Silberbrünnle, Haigerach Valley near Gengenbach, Central Black Forest, Germany (type locality)
Field-hunting tip
Where it forms: associated with organic-rich soils in protected cave environments. If you start seeing oxammite in float, you are in the right ground. Typical habit: tabular crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify gengenbachite?+
Where is gengenbachite found?+
What rocks look like gengenbachite?+
What minerals are found with gengenbachite?+
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Find gengenbachite on the map
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