Haineaultite is an extremely rare mineral discovered in the alkaline igneous rocks of Mont Saint-Hilaire. It typically forms delicate, needle-like acicular crystals or radial sprays in small vugs, often requiring a microscope for proper identification.

Hardness

3-4

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent to translucent

mineralrare

Haineaultite

Hardness: 3-4
Luster: Vitreous
Streak: White
Transparency: Transparent to translucent

Is this haineaultite?

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 haineaultite with a known reference. Haineaultite sits at Mohs 3-4, 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: pale brown, brown, orange yellow.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: fan shaped, prismatic.

Often confused with

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

Often found alongside haineaultite

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

All properties

Chemical formula: (Na,Ca)₅Ca(Ti,Nb)₅Si₁₂O₃₄(OH,F)₈·5H₂O
Mohs hardness: 3-4
Density: 2.28 g/cm³
Colors: Pale brown Brown Orange yellow
Streak: White
Luster: Vitreous
Transparency: Transparent to translucent
Crystal system: Orthorhombic
Crystal habit: Fan shaped, prismatic
Cleavage: Distinct to good on {100}, {010}, and {001}
Rarity: Rare
Uses: Collector
Host rock: A late-stage mineral in altered marble zenoliths and breccia in a complex peralkaline intrusion (nepheline and sodalite syenties)

Where rockhounds find haineaultite

Classic worldwide localities

Poudrette quarry, Mont Saint-Hilaire, Rouville County, Quebec, Canada

Field-hunting tip

Where it forms: A late-stage mineral in altered marble zenoliths and breccia in a complex peralkaline intrusion (nepheline and sodalite syenties). If you start seeing quartz, calcite, sodic amphibole in float, you are in the right ground. Typical habit: fan shaped, prismatic. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify haineaultite?+

Mohs hardness is 3-4. Luster: vitreous. The streak is white. Common colors include pale brown, brown, orange yellow.

Where is haineaultite found?+

Notable localities include Poudrette quarry, Mont Saint-Hilaire, Rouville County, Quebec, Canada.

What rocks look like haineaultite?+

Haineaultite is most often confused with Gittinsite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with haineaultite?+

Haineaultite commonly co-occurs with Quartz, Calcite, Sodic amphibole, Pectolite, Fluorapophyllite, Vesuvianite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does haineaultite form in?+

Where it forms: A late-stage mineral in altered marble zenoliths and breccia in a complex peralkaline intrusion (nepheline and sodalite syenties). Working float back to the host body is the standard way to chase a fresh occurrence.

What is haineaultite used for?+

Haineaultite is used in collector.

Find haineaultite on the map

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