Carlfrancisite is a rare manganese arsenate mineral belonging to the dixenite group, typically occurring in metamorphosed manganese deposits. It is best identified by its brownish-red to black platy crystal habit and is primarily found in Swedish mining districts such as Långban.
Is this carlfrancisite?
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 carlfrancisite with a known reference. Carlfrancisite sits at Mohs 3.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Carlfrancisite leaves a brown streak.
- 3Read the lusterHold the specimen under a strong light. Carlfrancisite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: dark brown, brownish red, black.
- 5Look at form & habitCrystal system: trigonal. Typical habit: platy crystals, tabular aggregates.
Often confused with
Carlfrancisite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside carlfrancisite
Minerals reported to co-occur with carlfrancisite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mn²⁺₃(AsO₄)(AsO₃)(OH)₆
- Mohs hardness
- 3.5
- Density
- 4.24 g/cm³
- Streak
- Brown
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Platy Crystals, Tabular Aggregates
- Cleavage
- Perfect On {0001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Metamorphosed Iron-manganese Deposits
- Typical price
- $100-500 depending on specimen quality and rarity
Where rockhounds find carlfrancisite
Classic worldwide localities
- Jakobsberg Mine, Sweden
- Långban, Sweden
Field-hunting tip
Look in metamorphosed iron-manganese deposits country — that is the host setting where carlfrancisite typically forms. If you start seeing dixenite, kraisslite, calcite in float, you are in the right ground. Field specimens usually show a platy crystals, tabular aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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