Lalondeite is a rare silicate mineral primarily found in the nepheline syenite pegmatites of Mont Saint-Hilaire, Canada. It forms small, colorless to white prismatic crystals and is frequently associated with other rare alkaline minerals like serandite and pectolite. Due to its extremely limited locality, it is highly sought after by systematic mineral collectors.
Is this lalondeite?
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 lalondeite with a known reference. Lalondeite 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. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: pearly.
- 4Match the color rangeCompare against the expected color range: pink.
- 5Look at form & habitCrystal system: triclinic. Typical habit: irregular grains, subhedral crystals.
Often confused with
Lalondeite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Pectolite is the harder of the two (Mohs 4.5-5 vs. ~3); luster reads pearly on Lalondeite and silky, subvitreous on Pectolite.
How to tell apart: Serandite is the harder of the two (Mohs 5-5.5 vs. ~3); luster reads pearly on Lalondeite and vitreous to greasy; fibrous aggregates are dull to silky on Serandite.
Often found alongside lalondeite
Minerals reported to co-occur with lalondeite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Na,Ca)₆(Si₆O₁₅(OH)₂)(OH,F)₂·3H₂O
- Mohs hardness
- ~3
- Density
- 2.50 g/cm³
- Colors
- Streak
- White
- Luster
- Pearly
- Transparency
- Transparent
- Crystal system
- Triclinic
- Crystal habit
- Irregular grains, subhedral crystals
- Cleavage
- Perfect on {001}
- Fluorescence
- Violet-blue under SW UV; none under LW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A late-stage low-temperature hydrothermal mineral
Where rockhounds find lalondeite
Classic worldwide localities
- Poudrette quarry, Mont Saint-Hilaire, Quebec, Canada
Field-hunting tip
Where it forms: A late-stage low-temperature hydrothermal mineral. If you start seeing microcline, clinoamphibole, narsarssukite in float, you are in the right ground. Typical habit: irregular grains, subhedral crystals. Train your eye for that shape before scanning the outcrop.
Common questions
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Find lalondeite on the map
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