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, so Favreauite leaves light blue, Linarite leaves pale blue.
How to tell apart: Streak differs, so 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, 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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