Niobokupletskite is a rare member of the astrophyllite group, primarily distinguished by its high niobium content. It typically occurs as brown, platy or bladed crystals found within peralkaline syenites and pegmatites, often forming radiating clusters that resemble the related astrophyllite.

Hardness

3-4

Mohs

Luster

Vitreous

Transparency

Transparent

mineralrareKupletskite Group family

Niobokupletskite

Hardness: 3-4
Luster: Vitreous
Transparency: Transparent

Is this niobokupletskite?

4-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 niobokupletskite with a known reference. Niobokupletskite sits at Mohs 3-4, softer than the next harder reference, harder than the previous one.
2
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
3
Match the color range
Compare against the expected color range: brown, beige.
4
Look at form & habit
Crystal system: triclinic. Typical habit: platy, tabular.

Often confused with

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

How to tell apart: Luster reads vitreous on Niobokupletskite and submetallic, pearly, greasy on Astrophyllite.

Compare →

Often found alongside niobokupletskite

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

All properties

Chemical formula: K₂NaMn₇(Nb,Ti)₂Si₈O₂₄(O,OH,F)₇
Mohs hardness: 3-4
Density: 3.325 g/cm³
Colors: Brown Beige
Luster: Vitreous
Transparency: Transparent
Crystal system: Triclinic
Crystal habit: Platy, tabular
Cleavage: Perfect on {001}
Rarity: Rare
Uses: Collector
Host rock: A late-stage mineral in nepheline syenite pegmatite in an alkaline complex

Where rockhounds find niobokupletskite

Classic worldwide localities

Poudrette quarry, Mont Saint-Hilaire, Quebec, Canada

Field-hunting tip

Where it forms: A late-stage mineral in nepheline syenite pegmatite in an alkaline complex. If you start seeing kupletskite, aegirine, albite in float, you are in the right ground. Typical habit: platy, tabular. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify niobokupletskite?+

Mohs hardness is 3-4. Luster: vitreous. Common colors include brown, beige.

Where is niobokupletskite found?+

Notable localities include Poudrette quarry, Mont Saint-Hilaire, Quebec, Canada.

What rocks look like niobokupletskite?+

Niobokupletskite is most often confused with Kupletskite, Astrophyllite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with niobokupletskite?+

Niobokupletskite commonly co-occurs with Kupletskite, Aegirine, Albite, Analcime, Calicoancylite-, Calcite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does niobokupletskite form in?+

Where it forms: A late-stage mineral in nepheline syenite pegmatite in an alkaline complex. Working float back to the host body is the standard way to chase a fresh occurrence.

What is niobokupletskite used for?+

Niobokupletskite is used in collector.

Find niobokupletskite on the map

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