Carlfrancisite is a rare manganese magnesium iron hydroxide, typically yellowy orange to pale yellow. Associated minerals include alleghanyite, chlorite and pyrochroite. It was first described from the E15-11 south stope, Kombat mine, Otavi Valley, Namibia.
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, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: very pale yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to opalescent.
- 4Match the color rangeCompare against the expected color range: yellowy orange, pale yellow.
- 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.
How to tell apart: Streak differs, so Carlfrancisite leaves very pale yellow, Dixenite leaves brownish-red; luster reads vitreous to opalescent on Carlfrancisite and metallic to resinous on Dixenite.
How to tell apart: Streak differs, so Carlfrancisite leaves very pale yellow, Kraisslite leaves golden brown; luster reads vitreous to opalescent on Carlfrancisite and submetallic on Kraisslite.
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(Mn²⁺,Mg,Fe³⁺,Al)₄₂(As³⁺O₃)₂(As⁵⁺O₄)₄[(Si,As⁵⁺)O₄]₆[(As⁵⁺,Si)O₄]₂(OH)₄₂
- Mohs hardness
- 3
- Density
- 3.620 g/cm³
- Colors
- Yellowy orangePale yellow
- Streak
- Very pale yellow
- Luster
- Vitreous to opalescent
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Platy crystals, tabular aggregates
- Cleavage
- Perfect on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In metamorphosed lenses associated with Cu-Pb-Ag sulfide ores in feldspathic sandstone that have been reworked by late hydrothermal solutions
Where rockhounds find carlfrancisite
Classic worldwide localities
- E15-11 south stope, 11 level, at the 1241 m elevation, in the Asis West sector, Kombat mine, Otavi Valley, Namibia
Field-hunting tip
Where it forms: In metamorphosed lenses associated with Cu-Pb-Ag sulfide ores in feldspathic sandstone that have been reworked by late hydrothermal solutions. If you start seeing alleghanyite, chlorite, pyrochroite in float, you are in the right ground. Typical habit: platy crystals, tabular aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify carlfrancisite?+
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What rocks look like carlfrancisite?+
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Find carlfrancisite on the map
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