Kupletskite-(Cs) is a rare member of the astrophyllite group characterized by a high cesium content. It typically forms thin, bronze-colored platy crystals in alkaline igneous environments, often closely resembling its common relative astrophyllite.
Is this kupletskite-(cs)?
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-(cs) with a known reference. Kupletskite-(Cs) sits at Mohs 3 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Kupletskite-(Cs) leaves a yellowish-brown streak.
- 3Read the lusterHold the specimen under a strong light. Kupletskite-(Cs) typically shows a submetallic luster.
- 4Match the color rangeCompare against the expected color range: dark brown, reddish-brown, bronze.
- 5Look at form & habitCrystal system: triclinic. Typical habit: lamellar to platy crystals, often in radiating aggregates.
Often confused with
Kupletskite-(Cs) vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside kupletskite-(cs)
Minerals reported to co-occur with kupletskite-(cs). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (K,Cs)₂(Na,Mn)₇(Ti,Nb)₂(Si₄O₁₂)₂O₂(OH)₄F
- Mohs hardness
- 3
- Density
- 3.55 g/cm³
- Streak
- Yellowish-brown
- Luster
- Submetallic
- Transparency
- Translucent
- Crystal system
- Triclinic
- Crystal habit
- Lamellar to Platy Crystals, Often in Radiating Aggregates
- Cleavage
- Perfect On {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Alkaline Igneous Rocks, Pegmatites
- Typical price
- $50-300 per specimen
Where rockhounds find kupletskite-(cs)
Classic worldwide localities
- Kola Peninsula, Russia
- Mont Saint-Hilaire, Canada
Field-hunting tip
Look in alkaline igneous rocks, pegmatites country — that is the host setting where kupletskite-(cs) typically forms. If you start seeing microcline, nepheline, aegirine in float, you are in the right ground. Field specimens usually show a lamellar to platy crystals, often in radiating aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify kupletskite-(cs)?+
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Find kupletskite-(cs) on the map
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