Steedeite is a very rare silicate mineral discovered in the alkaline rocks of Mont Saint-Hilaire. It typically forms as delicate, white-to-colorless platy or radiating crystal aggregates nestled within vugs of larger intrusive formations.

Hardness

3.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Steedeite

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

No image

Is this steedeite?

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 steedeite with a known reference. Steedeite 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. Steedeite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Steedeite 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: triclinic. Typical habit: platy crystals, radiating clusters.

Often confused with

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

mineral

Pectolite

Mohs 4.5-5

How to tell apart: Pectolite is the harder of the two (Mohs 4.5-5 vs. 3.5); luster reads vitreous on Steedeite and vitreous to silky on Pectolite.

How to tell apart: Serandite is the harder of the two (Mohs 4.5-5 vs. 3.5).

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Often found alongside steedeite

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

All properties

Chemical formula: Na₄Mn₂Si₁₀O₂₄(OH)₂·4H₂O
Mohs hardness: 3.5
Density: 2.42 g/cm³
Colors: Colorless White
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Triclinic
Crystal habit: Platy Crystals, Radiating Clusters
Cleavage: Perfect {001}
Rarity: Rare
Uses: Collector
Host rock: Alkaline Igneous Complexes
Typical price: $50-300 per specimen

Where rockhounds find steedeite

Classic worldwide localities

Mont Saint-Hilaire, Quebec, Canada

Field-hunting tip

Look in alkaline igneous complexes country — that is the host setting where steedeite typically forms. If you start seeing eudialyte, microcline, nepheline in float, you are in the right ground. Field specimens usually show a platy crystals, radiating clusters habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify steedeite?+

Mohs hardness is 3.5. It typically shows a vitreous luster. The streak is white. Common colors include colorless, white.

Where is steedeite found?+

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

How much is steedeite 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 rocks look like steedeite?+

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

What minerals are found with steedeite?+

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

What kind of rock does steedeite form in?+

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

What is steedeite used for?+

Steedeite is used in collector.

Find steedeite on the map

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