Fabrièsite is a very rare phosphate mineral typically occurring as small, clear, tabular crystals. It is best known from the unique alkaline environment of the Mont Saint-Hilaire complex in Quebec, where it forms in vugs associated with other rare minerals.

Hardness

~5-5.5

Mohs

Luster

Vitreous to greasy

Streak

White

Transparency

Transparent

mineralrareGorceixite Group family

Fabrièsite

Hardness: ~5-5.5
Luster: Vitreous to greasy
Streak: White
Transparency: Transparent

Is this fabrièsite?

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 fabrièsite with a known reference. Fabrièsite sits at Mohs ~5-5.5, 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 greasy.
4
Match the color range
Compare against the expected color range: white, yellow.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: tabular crystals.

Often confused with

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

Often found alongside fabrièsite

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

All properties

Chemical formula: Na₃Al₃Si₃O₁₂·2H₂O
Mohs hardness: ~5-5.5
Density: 2.386 g/cm³
Colors: White Yellow
Streak: White
Luster: Vitreous to greasy
Transparency: Transparent
Crystal system: Orthorhombic
Crystal habit: Tabular crystals
Rarity: Rare
Uses: Collector
Host rock: In serpentinized peridotite and related to the hydration of trinepheline during the late stage of metamorphism along veins in a jadeite deposit

Where rockhounds find fabrièsite

Classic worldwide localities

Tawmaw-Hpakant Jade Tract, Hpakant Township, Mohnyin District, Kachin State, Myanmar

Field-hunting tip

Where it forms: In serpentinized peridotite and related to the hydration of trinepheline during the late stage of metamorphism along veins in a jadeite deposit. If you start seeing nepheline, trinepheline, banalsite in float, you are in the right ground. Typical habit: tabular crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify fabrièsite?+

Mohs hardness is ~5-5.5. Luster: vitreous to greasy. The streak is white. Common colors include white, yellow.

Where is fabrièsite found?+

Notable localities include Tawmaw-Hpakant Jade Tract, Hpakant Township, Mohnyin District, Kachin State, Myanmar.

What rocks look like fabrièsite?+

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

What minerals are found with fabrièsite?+

Fabrièsite commonly co-occurs with Nepheline, Trinepheline, Banalsite, Stronalsite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does fabrièsite form in?+

Where it forms: In serpentinized peridotite and related to the hydration of trinepheline during the late stage of metamorphism along veins in a jadeite deposit. Working float back to the host body is the standard way to chase a fresh occurrence.

What is fabrièsite used for?+

Fabrièsite is used in collector.

Find fabrièsite on the map

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