Kupletskite is a rare silicate mineral belonging to the astrophyllite group, often appearing as distinct dark, platy, or radiating blades. It is primarily found in alkaline pegmatites and is highly prized by collectors for its aesthetic crystal formations and its close chemical relationship to the more common astrophyllite.
Is this kupletskite?
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 kupletskite with a known reference. Kupletskite sits at Mohs 3-4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brown.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: yellow brown, black, black brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: acicular, tabular.
Often confused with
Kupletskite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Kupletskite leaves brown, Astrophyllite leaves golden; luster reads vitreous on Kupletskite and submetallic, pearly, greasy on Astrophyllite.
How to tell apart: Streak differs, so Kupletskite leaves brown, Niobophyllite leaves yellowish-brown.
Often found alongside kupletskite
Minerals reported to co-occur with kupletskite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K₂NaMn₇Ti₂(Si₄O₁₂)₂O₂(OH)₄F
- Mohs hardness
- 3-4
- Density
- 3.20-3.36 g/cm³
- Streak
- Brown
- Luster
- Vitreous
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Acicular, tabular
- Cleavage
- Perfect on {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In the natrolite-rich central part and in the wall rocks of nepheline syenite pegmatites in a differentiated alkalic massif (Lovozero massif, Russia)
Where rockhounds find kupletskite
Classic worldwide localities
- Granite Mountain, near Little Rock, Pulaski Co., and the Diamond Jo quarry, Magnet Cove, Hot Spring Co., Arkansas, USA
- Oktyabr massif, eastern Azov area, Ukraine
- Gjerdingen, north of Oslo, Norway
- Mont Saint-Hilaire, Quebec, Canada
Field-hunting tip
Where it forms: In the natrolite-rich central part and in the wall rocks of nepheline syenite pegmatites in a differentiated alkalic massif (Lovozero massif, Russia). If you start seeing manganoan pectolite, neptunite, microcline in float, you are in the right ground. Typical habit: acicular, tabular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify kupletskite?+
Where is kupletskite found?+
What rocks look like kupletskite?+
What minerals are found with kupletskite?+
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Find kupletskite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
