Karupmøllerite-Ca is a complex rare-earth mineral belonging to the Labuntsovite group, typically found in alkaline pegmatites. Collectors usually search for its characteristic yellow to brown prismatic crystals embedded in microcline or associated with other rare alkaline minerals.

Hardness

Mohs

Luster

Vitreous to dull

Streak

White

Transparency

Translucent

mineralrareLabuntsovite Group family

Karupmøllerite-Ca

Hardness: 5
Luster: Vitreous to dull
Streak: White
Transparency: Translucent

No image

Is this karupmøllerite-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 karupmøllerite-ca with a known reference. Karupmøllerite-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 to dull.
4
Match the color range
Compare against the expected color range: white, grayish white, pinkish white.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: platy, pseudomorphous.

Often confused with

Karupmøllerite-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 to dull on Karupmøllerite-Ca and greasy on Labuntsovite.

Often found alongside karupmøllerite-ca

Minerals reported to co-occur with karupmøllerite-ca. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: (Na,Ca,K)₄(Ti,Nb)₄(Si₄O₁₂)₂(OH,O)₄·5H₂O
Mohs hardness: 5
Density: 2.71 g/cm³
Colors: White Grayish white Pinkish white
Streak: White
Luster: Vitreous to dull
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Platy, pseudomorphous
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Found replacing epistolite which was derived from vuonnemite. (labuntsovite group; structure refined)

Where rockhounds find karupmøllerite-ca

Classic worldwide localities

Ilimaussaq alkaline complex, South Greenland (type locality)

Field-hunting tip

Where it forms: Found replacing epistolite which was derived from vuonnemite. (labuntsovite group; structure refined). If you start seeing aegirine, microcline, albite in float, you are in the right ground. Typical habit: platy, pseudomorphous. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify karupmøllerite-ca?+

Mohs hardness is 5. Luster: vitreous to dull. The streak is white. Common colors include white, grayish white, pinkish white.

Where is karupmøllerite-ca found?+

Notable localities include Ilimaussaq alkaline complex, South Greenland (type locality).

What rocks look like karupmøllerite-ca?+

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

What minerals are found with karupmøllerite-ca?+

Karupmøllerite-Ca commonly co-occurs with Aegirine, Microcline, Albite, Eudialyte, Arfvedsonite. Spotting any of these in float or country rock is a useful trip signal.

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

Where it forms: Found replacing epistolite which was derived from vuonnemite. (labuntsovite group; structure refined). Working float back to the host body is the standard way to chase a fresh occurrence.

What is karupmøllerite-ca used for?+

Karupmøllerite-Ca is used in collector.

Find karupmøllerite-ca on the map

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