Silinaite is a rare phyllosilicate mineral that typically forms as white, platy crystals in alkaline igneous complexes. It is most famously found in the miarolitic cavities of Mont Saint-Hilaire, where it occurs alongside a variety of exotic rare-earth minerals. Due to its softness and perfect cleavage, specimens should be handled with care to prevent damage.

Hardness

~4.5

Mohs

Luster

Vitreous to earthy

Streak

White

Transparency

Transparent to translucent, opaque

mineralrare

Silinaite

Hardness: ~4.5
Luster: Vitreous to earthy
Streak: White
Transparency: Transparent to translucent, opaque

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Is this silinaite?

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 silinaite with a known reference. Silinaite 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. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous to earthy.
4
Match the color range
Compare against the expected color range: white, colorless.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: platy crystals.

Often confused with

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

How to tell apart: Luster reads vitreous to earthy on Silinaite and silky on Gonnardite.

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Often found alongside silinaite

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

All properties

Chemical formula: NaLiSi₂O₅·2H₂O
Mohs hardness: ~4.5
Density: 2.24 g/cm³
Colors: White Colorless
Streak: White
Luster: Vitreous to earthy
Transparency: Transparent to translucent, opaque
Crystal system: Monoclinic
Crystal habit: Platy crystals
Cleavage: {001}, perfect; {010}, good; {110}, distinct
Rarity: Rare
Uses: Collector
Host rock: In sodalite syenite xenoliths in nepheline syenite in an intrusive alkalic gabbro-syenite complex

Where rockhounds find silinaite

Classic worldwide localities

Mont Saint-Hilaire, Quebec, Canada

Field-hunting tip

Where it forms: In sodalite syenite xenoliths in nepheline syenite in an intrusive alkalic gabbro-syenite complex. If you start seeing ussingite, terskite-, sérandite in float, you are in the right ground. Typical habit: platy crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify silinaite?+

Mohs hardness is ~4.5. Luster: vitreous to earthy. The streak is white. Common colors include white, colorless.

Where is silinaite found?+

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

What rocks look like silinaite?+

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

What minerals are found with silinaite?+

Silinaite commonly co-occurs with Ussingite, Terskite-, Sérandite, Vuonnemite, Halite, Villiaumite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does silinaite form in?+

Where it forms: In sodalite syenite xenoliths in nepheline syenite in an intrusive alkalic gabbro-syenite complex. Working float back to the host body is the standard way to chase a fresh occurrence.

What is silinaite used for?+

Silinaite is used in collector.

Find silinaite on the map

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