Petarasite is a rare zirconium silicate mineral known for forming sharp, vitreous, yellowish-brown crystals in alkaline environments. It is most famously found in the peralkaline pegmatites of Mont Saint-Hilaire, where it is highly sought after by mineral enthusiasts. Collectors typically look for its distinct monoclinic prismatic habit associated with other rare-earth and alkaline silicate minerals.
Is this petarasite?
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 petarasite with a known reference. Petarasite sits at Mohs 5-5.5, 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.
- 4Match the color rangeCompare against the expected color range: brownish yellow, greenish yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: euhedral crystals, irregular grains.
Often confused with
Petarasite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside petarasite
Minerals reported to co-occur with petarasite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₅Zr₂Si₆O₁₈(Cl,OH)·2H₂O
- Mohs hardness
- 5-5.5
- Density
- 2.88 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent to translucent or opaque
- Crystal system
- Monoclinic
- Crystal habit
- Euhedral crystals, irregular grains
- Cleavage
- Perfect on {110}, very good on {010}, and distinct on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In a biotite-microcline xenolith and in pegmatitic veins in a nepheline syenite in an intrusive alkalic gabbro-syenite complex
Where rockhounds find petarasite
Classic worldwide localities
- Mont Saint-Hilaire, Quebec, Canada
Field-hunting tip
Where it forms: In a biotite-microcline xenolith and in pegmatitic veins in a nepheline syenite in an intrusive alkalic gabbro-syenite complex. If you start seeing biotite, microcline, catapleiite in float, you are in the right ground. Typical habit: euhedral crystals, irregular grains. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify petarasite?+
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What rocks look like petarasite?+
What minerals are found with petarasite?+
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Find petarasite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
