Gaultite is a rare sodium zinc silicate. It was approved as a distinct mineral species in 1992, from material found at the Poudrette quarry, Mont Saint-Hilaire, Rouville County, Quebec, Canada.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Gaultite

Gaultite is a rare sodium zinc silicate. It was approved as a distinct mineral species in 1992, from material found at the Poudrette quarry, Mont Saint-Hilaire, Rouville County, Quebec, Canada.

Hardness: 6
Luster: Vitreous
Streak: White
Transparency: Transparent

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Is this gaultite?

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 gaultite with a known reference. Gaultite sits at Mohs 6, 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: colorless, pale mauve.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: crystalline.

Often confused with

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

Often found alongside gaultite

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

All properties

Chemical formula: Na₄Zn₂Si₇O₁₈·5H₂O
Mohs hardness: 6
Density: 2.52 g/cm³
Colors: ColorlessPale mauve
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Orthorhombic
Crystal habit: Crystalline
Cleavage: Perfect on {101}; perfect on {010}; poor on {021}
Fluorescence: Bright apple green under SW UV
Rarity: Rare
Uses: Collector
Host rock: In a cavity in a sodalite syenite xenolith near a contact of hornfels and nepheline-sodalite syenite

Where rockhounds find gaultite

Classic worldwide localities

Poudrette Quarry, Mont Saint-Hilaire, Rouville County, Quebec, Canada (type locality)

Field-hunting tip

Where it forms: In a cavity in a sodalite syenite xenolith near a contact of hornfels and nepheline-sodalite syenite. If you start seeing sodalite, analcime, microcline in float, you are in the right ground. Typical habit: crystalline. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify gaultite?+

Mohs hardness is 6. Luster: vitreous. The streak is white. Common colors include colorless, pale mauve.

Where is gaultite found?+

Notable localities include Poudrette Quarry, Mont Saint-Hilaire, Rouville County, Quebec, Canada (type locality).

What rocks look like gaultite?+

Gaultite is most often confused with Sodalite, Analcime. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with gaultite?+

Gaultite commonly co-occurs with Sodalite, Analcime, Microcline, Aegirine, Eudialyte. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does gaultite form in?+

Where it forms: In a cavity in a sodalite syenite xenolith near a contact of hornfels and nepheline-sodalite syenite. Working float back to the host body is the standard way to chase a fresh occurrence.

What is gaultite used for?+

Gaultite is used in collector.

Find gaultite on the map

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