Gjerdingenite-Fe is a rare member of the complex labuntsovite group typically found as small, sharp prismatic crystals. It is most often identified in the cavities of alkaline pegmatites, requiring microscopic examination for positive field identification due to its similarity to other group members.
Is this gjerdingenite-fe?
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 gjerdingenite-fe with a known reference. Gjerdingenite-Fe sits at Mohs 5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white to faint yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to waxy.
- 4Match the color rangeCompare against the expected color range: yellow, pale yellow, yellow orange.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: aggregates, lath, prismatic.
Often confused with
Gjerdingenite-Fe vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside gjerdingenite-fe
Minerals reported to co-occur with gjerdingenite-fe. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K₂Fe(Nb,Ti)₄(Si₄O₁₂)₂(O,OH)₄·6H₂O
- Mohs hardness
- 5
- Density
- 2.82 g/cm³
- Streak
- White to faint yellow
- Luster
- Vitreous to waxy
- Transparency
- Translucent to transparent
- Crystal system
- Monoclinic
- Crystal habit
- Aggregates, lath, prismatic
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In miarolitic cavities in a sodic granite
Where rockhounds find gjerdingenite-fe
Classic worldwide localities
- Gjerdingselva, Lunnar, Pooland, Norway (type locality)
Field-hunting tip
Where it forms: In miarolitic cavities in a sodic granite. If you start seeing quartz, orthoclase, albite in float, you are in the right ground. Typical habit: aggregates, lath, prismatic. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify gjerdingenite-fe?+
Where is gjerdingenite-fe found?+
What rocks look like gjerdingenite-fe?+
What minerals are found with gjerdingenite-fe?+
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Find gjerdingenite-fe on the map
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