Hilairite is a rare zirconium silicate mineral discovered in the unique alkaline environment of Mont Saint-Hilaire. Collectors look for its characteristic small, sharp, rhombohedral crystals typically found in vugs within nepheline syenite pegmatites.
Is this hilairite?
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 hilairite with a known reference. Hilairite sits at Mohs >4, 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: vitreous to porcelaneous.
- 4Match the color rangeCompare against the expected color range: light brown.
- 5Look at form & habitCrystal system: trigonal. Typical habit: rhombohedral crystals.
Often confused with
Hilairite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside hilairite
Minerals reported to co-occur with hilairite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₂ZrSi₃O₉·3H₂O
- Mohs hardness
- >4
- Density
- 2.724 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous to porcelaneous
- Transparency
- Transparent to opaque
- Crystal system
- Trigonal
- Crystal habit
- Rhombohedral crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In miarolitic cavities and altered pegmatite dikes in nepheline syenite in an intrusive alkalic gabbro-syenite complex (Mont Saint-Hilaire, Canada)
Where rockhounds find hilairite
Classic worldwide localities
- Mont Saint-Hilaire, and in the Strange Lake complex, Quebec, Canada
- Bratthagen, near Larvik, Norway
- Mt. Alluaiv, Lovozero massif, Kola Peninsula, Russia
Field-hunting tip
Where it forms: In miarolitic cavities and altered pegmatite dikes in nepheline syenite in an intrusive alkalic gabbro-syenite complex (Mont Saint-Hilaire, Canada). If you start seeing catapleiite, elpidite, gaidonnayite in float, you are in the right ground. Typical habit: rhombohedral crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify hilairite?+
Where is hilairite found?+
What rocks look like hilairite?+
What minerals are found with hilairite?+
What kind of rock does hilairite form in?+
What is hilairite used for?+
Find hilairite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
