Dawsonite typically forms as delicate, radiating tufts or blades of white acicular crystals lining vugs in igneous or sedimentary rocks. It is most famous for its occurrences in the limestone quarries of the Montreal area, where it is found associated with various other carbonates and zeolites.
Is this dawsonite?
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 dawsonite with a known reference. Dawsonite 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: vitreous, silky in fibrous aggregates.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: acicular, encrustations, radial.
Often confused with
Dawsonite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside dawsonite
Minerals reported to co-occur with dawsonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaAl(CO₃)(OH)₂
- Mohs hardness
- 3
- Density
- 2.436 g/cm³
- Streak
- White
- Luster
- Vitreous, silky in fibrous aggregates
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Acicular, encrustations, radial
- Cleavage
- {110}, perfect
- Rarity
- Uncommon
- Uses
- Collector, Scientific research
- Host rock
- Coating vug walls and fractures in hydrothermally altered feldspathic dikes and hornfels associated with nepheline syenite (Mont Saint-Bruno, Canada)
Where rockhounds find dawsonite
1 mapped spotsClassic worldwide localities
- Green River Formation, Colorado and Wyoming, USA
- Mont Saint-Bruno and as Mont Saint-Hilaire, Quebec, Canada
- Saint-Amable, Quebec, Canada
- Bancroft, Ontario, Canada
- Pian Castagnaio and Santa Fiora, near Mt. Amiata, Siena, Tuscany, Italy
- Monte Tondo, Terlano, Bolzano, Italy
Field-hunting tip
Where it forms: Coating vug walls and fractures in hydrothermally altered feldspathic dikes and hornfels associated with nepheline syenite (Mont Saint-Bruno, Canada). If you start seeing fluorite, calcite, dolomite in float, you are in the right ground. Typical habit: acicular, encrustations, radial. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Utah. Start trip planning there.
Common questions
How do you identify dawsonite?+
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Can I find dawsonite in the United States?+
What rocks look like dawsonite?+
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Find dawsonite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
