Favreauite is an incredibly rare lead-bismuth-copper selenite mineral known almost exclusively from the Poudrette quarry at Mont Saint-Hilaire. It typically forms small, bright blue, translucent tabular crystals or crusts in vugs within alkaline igneous rocks. Collectors prize this species for its intense color and status as a type-locality rarity.
Is this favreauite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch favreauite with a known reference. Favreauite sits at Mohs 2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Favreauite leaves a light blue streak.
- 3Read the lusterHold the specimen under a strong light. Favreauite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: blue, greenish-blue.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: tabular crystals, crusts, aggregates.
Often confused with
Favreauite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Favreauite leaves light blue, Linarite leaves pale blue.
How to tell apart: Streak differs — Favreauite leaves light blue, Chalcoalumite leaves white; luster reads vitreous on Favreauite and pearly on Chalcoalumite.
Often found alongside favreauite
Minerals reported to co-occur with favreauite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- PbBiCu₆(SeO₃)₄(OH)₁₂·2H₂O
- Mohs hardness
- 2
- Density
- 4.15 g/cm³
- Colors
- Streak
- Light Blue
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Tetragonal
- Crystal habit
- Tabular Crystals, Crusts, Aggregates
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Alkaline Igneous Intrusions
- Typical price
- $100-500 thumbnail
Where rockhounds find favreauite
Classic worldwide localities
- Poudrette quarry, Mont Saint-Hilaire, Canada
Field-hunting tip
Look in alkaline igneous intrusions country — that is the host setting where favreauite typically forms. If you start seeing galena, bornite, hausmannite in float, you are in the right ground. Field specimens usually show a tabular crystals, crusts, aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find favreauite on the map
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