Mahnertite is a rare member of the gismondine group found primarily in the nepheline syenite pegmatites of Mont Saint-Hilaire. It typically occurs as small, clear, tabular crystals associated with other rare alkaline suite minerals.

Hardness

4-5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareGismondine Group family

Mahnertite

Hardness: 4-5
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this mahnertite?

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 mahnertite with a known reference. Mahnertite sits at Mohs 4-5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Mahnertite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Mahnertite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: colorless, white.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: tabular crystals.

Often found alongside mahnertite

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

All properties

Chemical formula: (Na,Ca)₈(Si,Al)₁₂O₂₄(OH)₄·4H₂O
Mohs hardness: 4-5
Density: 2.16 g/cm³
Colors: Colorless White
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Tabular Crystals
Cleavage: Distinct On {010}
Rarity: Rare
Uses: Collector
Host rock: Alkaline Igneous Rocks
Typical price: $50-300 per specimen

Where rockhounds find mahnertite

Classic worldwide localities

Mont Saint-Hilaire, Quebec, Canada

Field-hunting tip

Look in alkaline igneous rocks country — that is the host setting where mahnertite typically forms. If you start seeing aegirine, analcime, serandite in float, you are in the right ground. Field specimens usually show a tabular crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify mahnertite?+

Mohs hardness is 4-5. It typically shows a vitreous luster. The streak is white. Common colors include colorless, white.

Where is mahnertite found?+

Notable localities include Mont Saint-Hilaire, Quebec, Canada.

How much is mahnertite worth?+

Typical asking prices fall in the range of $50-300 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What minerals are found with mahnertite?+

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

What kind of rock does mahnertite form in?+

Mahnertite typically forms in alkaline igneous rocks. Working float back to the host body is the standard way to chase a fresh occurrence.

What is mahnertite used for?+

Mahnertite is used in collector.

Find mahnertite on the map

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