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.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent to translucent

mineralrareLabuntsovite Group family

Gjerdingenite-Ca

Hardness: 5
Luster: Vitreous
Streak: White
Transparency: Transparent to translucent

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Is this gjerdingenite-ca?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try 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.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: white, pale brown, pinkish brown.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: pseudomorphous.

Often confused with

Gjerdingenite-Ca vs. its common look-alikes, and how to tell them apart in the field.

mineral

Labuntsovite

Mohs 6

How to tell apart: Labuntsovite is the harder of the two (Mohs 6 vs. 5); luster reads vitreous on Gjerdingenite-Ca and greasy on Labuntsovite.

How to tell apart: Leucosphenite is the harder of the two (Mohs 6-6.5 vs. 5).

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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: 2.79 g/cm³
Colors: White Pale brown Pinkish brown
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-ca

Classic worldwide localities

Pegmatite #61 at Mount Karnasurt, Lovozero massif, Kola Peninsula, Russia

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, natrolite, 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-ca?+

Mohs hardness is 5. Luster: vitreous. The streak is white. Common colors include white, pale brown, pinkish brown.

Where is gjerdingenite-ca found?+

Notable localities include Pegmatite #61 at Mount Karnasurt, Lovozero massif, Kola Peninsula, Russia.

What rocks look like gjerdingenite-ca?+

Gjerdingenite-Ca is most often confused with Labuntsovite, Leucosphenite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with gjerdingenite-ca?+

Gjerdingenite-Ca commonly co-occurs with Microcline, Natrolite, Aegirine, Organovaite-Mn, Organovaite-Zn, Beryllite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does gjerdingenite-ca form in?+

Where it forms: As alteration of vuonnemite formed in hydrothermal assemblages of peralkaline pegmatites related to agpaitic feldspathoidal syenites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is gjerdingenite-ca used for?+

Gjerdingenite-Ca is used in collector.

Find gjerdingenite-ca on the map

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