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, 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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