Gjerdingenite-Na is a rare member of the labuntsovite group typically found as small, tabular to prismatic crystals in alkaline pegmatites. It is best identified by its association with rare-earth minerals in syenitic environments and is primarily sought after by advanced collectors of complex silicate species.
Is this gjerdingenite-na?
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-na with a known reference. Gjerdingenite-Na 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.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: colorless, pale pink.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: pseudomorphous.
Often confused with
Gjerdingenite-Na vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Labuntsovite is the harder of the two (Mohs 6 vs. 5); luster reads vitreous on Gjerdingenite-Na and greasy on Labuntsovite.
How to tell apart: Gjerdingenite-Na is noticeably harder (Mohs 5 vs. 3-4); streak differs, so Gjerdingenite-Na leaves white, Kupletskite leaves brown.
How to tell apart: Gjerdingenite-Na is noticeably harder (Mohs 5 vs. 3); streak differs, so Gjerdingenite-Na leaves white, Astrophyllite leaves golden; luster reads vitreous on Gjerdingenite-Na and submetallic, pearly, greasy on Astrophyllite.
Often found alongside gjerdingenite-na
Minerals reported to co-occur with gjerdingenite-na. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Na,K,H₂O)₄(Ti,Nb)₄(Si₄O₁₂)₂(O,OH)₄·5H₂O
- Mohs hardness
- 5
- Density
- 2.71 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Monoclinic
- Crystal habit
- Pseudomorphous
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- As alteration of vuonnemite formed in hydrothermal assemblages of peralkaline pegmatites related to agpaitic feldspathoidal syenites
Where rockhounds find gjerdingenite-na
Classic worldwide localities
- East Hill suite, De-Mix quarry (now part of the Poudrette quarry), Mont Saint-Hilaire, Quebec, Canada
Field-hunting tip
Where it forms: As alteration of vuonnemite formed in hydrothermal assemblages of peralkaline pegmatites related to agpaitic feldspathoidal syenites. If you start seeing microcline, albite, aegirine in float, you are in the right ground. Typical habit: pseudomorphous. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify gjerdingenite-na?+
Where is gjerdingenite-na found?+
What rocks look like gjerdingenite-na?+
What minerals are found with gjerdingenite-na?+
What kind of rock does gjerdingenite-na form in?+
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Find gjerdingenite-na on the map
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