Carletonite is an exceptionally rare phyllosilicate mineral known almost exclusively from the Poudrette quarry at Mont Saint-Hilaire. It is prized by collectors for its stunning blue color and well-formed tetragonal tabular crystals that often exhibit a pearly luster on cleavage surfaces.
Is this carletonite?
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 carletonite with a known reference. Carletonite sits at Mohs 4-4.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Carletonite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Carletonite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: blue, colorless, white, pink.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: tabular crystals.
Often confused with
Carletonite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside carletonite
Minerals reported to co-occur with carletonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KNa₄Ca₄Si₈O₁₈(CO₃)₄(F,OH)·H₂O
- Mohs hardness
- 4-4.5
- Density
- 2.45 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Tetragonal
- Crystal habit
- Tabular Crystals
- Cleavage
- Perfect On {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Alkaline Igneous Intrusions
- Typical price
- $50-500 thumbnail, $1000+ cabinet specimen
Where rockhounds find carletonite
Classic worldwide localities
- Mont Saint-Hilaire, Quebec, Canada
Field-hunting tip
Look in alkaline igneous intrusions country — that is the host setting where carletonite typically forms. If you start seeing aegirine, analcime, leucosphenite in float, you are in the right ground. Field specimens usually show a tabular crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find carletonite on the map
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