Weloganite is a highly sought-after rare carbonate mineral found primarily in the unique alkaline rocks of Mont Saint-Hilaire. Collectors prize its distinct pseudo-hexagonal bipyramidal crystal form and its diagnostic bright fluorescence under ultraviolet light.

Hardness

3.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent to translucent

mineralrare

Weloganite

Hardness: 3.5
Luster: Vitreous
Streak: White
Transparency: Transparent to translucent

Is this weloganite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch weloganite with a known reference. Weloganite sits at Mohs 3.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: white, lemon yellow, amber, colorless.
5
Look at form & habit
Crystal system: triclinic. Typical habit: massive, pseudo hexagonal.

Often confused with

Weloganite vs. its common look-alikes, and how to tell them apart in the field.

How to tell apart: Quartz is the harder of the two (Mohs 7 vs. 3.5).

Often found alongside weloganite

Minerals reported to co-occur with weloganite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: Sr₃Na₂Zr(CO₃)₆·3H₂O
Mohs hardness: 3.5
Density: 3.20-3.22 g/cm³
Colors: White Lemon yellow Amber Colorless
Streak: White
Luster: Vitreous
Transparency: Transparent to translucent
Crystal system: Triclinic
Crystal habit: Massive, pseudo hexagonal
Cleavage: Perfect on pseudo-{0001}
Fluorescence: Bright yellow to white under SW/LW UV
Rarity: Rare
Uses: Collector, Scientific research
Host rock: In an alkalic sill (Francon quarry, Canada); associated with an intrusive alkalic gabbro-syenite complex (Mont Saint-Hilaire, Canada)

Where rockhounds find weloganite

Classic worldwide localities

Francon quarry, Montreal Island, Montreal, Canada
A limestone quarry 15 km east, Canada
Mont Saint-Hilaire, Quebec, Canada

Field-hunting tip

Where it forms: In an alkalic sill (Francon quarry, Canada); associated with an intrusive alkalic gabbro-syenite complex (Mont Saint-Hilaire, Canada). If you start seeing calcite, quartz, dawsonite in float, you are in the right ground. Typical habit: massive, pseudo hexagonal. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify weloganite?+

Mohs hardness is 3.5. Luster: vitreous. The streak is white. Common colors include white, lemon yellow, amber, colorless.

Where is weloganite found?+

Notable localities include Francon quarry, Montreal Island, Montreal, Canada; A limestone quarry 15 km east, Canada; Mont Saint-Hilaire, Quebec, Canada.

What rocks look like weloganite?+

Weloganite is most often confused with Dresserite, Quartz, Calcite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with weloganite?+

Weloganite commonly co-occurs with Calcite, Quartz, Dawsonite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does weloganite form in?+

Where it forms: In an alkalic sill (Francon quarry, Canada); associated with an intrusive alkalic gabbro-syenite complex (Mont Saint-Hilaire, Canada). Working float back to the host body is the standard way to chase a fresh occurrence.

What is weloganite used for?+

Weloganite is used in collector, scientific research.

Find weloganite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.