Gjerdingenite-Ca is a rare member of the labuntsovite group typically found as small, prismatic, honey-yellow to brownish crystals. It is primarily identified in alkaline pegmatite environments, specifically associated with the unique mineralogy of the Langesundsfjord region in Norway.
Is this gjerdingenite-ca?
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-ca with a known reference. Gjerdingenite-Ca 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. Gjerdingenite-Ca leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Gjerdingenite-Ca typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, brown, orange.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals.
Often confused with
Gjerdingenite-Ca vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside gjerdingenite-ca
Minerals reported to co-occur with gjerdingenite-ca. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K₂Ca(Ti,Nb)₄(Si₄O₁₂)₂O(OH)₄·5H₂O
- Mohs hardness
- 5
- Density
- 2.9-3.1 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic Crystals
- Cleavage
- Distinct
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Alkaline Pegmatites
- Typical price
- $50-300 per specimen
Where rockhounds find gjerdingenite-ca
Classic worldwide localities
- Langesundsfjord, Norway
- Kola Peninsula, Russia
Field-hunting tip
Look in alkaline pegmatites country — that is the host setting where gjerdingenite-ca typically forms. If you start seeing aegirine, microcline, nepheline in float, you are in the right ground. Field specimens usually show a prismatic crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify gjerdingenite-ca?+
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