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

Submetallic

Streak

Brown

Transparency

Opaque

mineralrareKupletskite Group family

Niobokupletskite

Hardness: 3-4
Luster: Submetallic
Streak: Brown
Transparency: Opaque

Is this niobokupletskite?

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 niobokupletskite with a known reference. Niobokupletskite sits at Mohs 3-4 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Niobokupletskite leaves a brown streak.
3
Read the luster
Hold the specimen under a strong light. Niobokupletskite typically shows a submetallic luster.
4
Match the color range
Compare against the expected color range: brown, dark brown, reddish-brown.
5
Look at form & habit
Crystal system: triclinic. Typical habit: platy crystals, radial aggregates.

Often confused with

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

How to tell apart: Streak differs — Niobokupletskite leaves brown, Astrophyllite leaves golden-brown.

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: 3.3-3.4 g/cm³
Colors: Brown Dark Brown Reddish-brown
Streak: Brown
Luster: Submetallic
Transparency: Opaque
Crystal system: Triclinic
Crystal habit: Platy Crystals, Radial Aggregates
Cleavage: Perfect On {001}
Rarity: Rare
Uses: Collector
Host rock: Alkaline Igneous Rocks
Typical price: $50-300 per specimen

Where rockhounds find niobokupletskite

Classic worldwide localities

Lovozero Massif, Russia
Kola Peninsula, Russia

Field-hunting tip

Look in alkaline igneous rocks country — that is the host setting where niobokupletskite typically forms. If you start seeing aegirine, nepheline, microcline in float, you are in the right ground. Field specimens usually show a platy crystals, radial aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify niobokupletskite?+

Mohs hardness is 3-4. It typically shows a submetallic luster. The streak is brown. Common colors include brown, dark brown, reddish-brown.

Where is niobokupletskite found?+

Notable localities include Lovozero Massif, Russia; Kola Peninsula, Russia.

How much is niobokupletskite worth?+

Typical asking prices fall in the range of $50-300 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

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 Aegirine, Nepheline, Microcline, Eudialyte. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does niobokupletskite form in?+

Niobokupletskite typically forms in alkaline igneous rocks. 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

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.