Francisite is an incredibly rare copper bismuth selenite chloride mineral known primarily from the Centenario Mine in Bolivia. It typically forms attractive, small, green to blue-green platy crystals within oxidized ore zones. Collectors value it for its unusual composition and strictly limited locality occurrences.
Is this francisite?
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 francisite with a known reference. Francisite 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. Francisite leaves a light green streak.
- 3Read the lusterHold the specimen under a strong light. Francisite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: green, blue-green.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: platy crystals, crusts.
Often confused with
Francisite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Francisite is noticeably harder (Mohs 3.5 vs. 2.5); streak differs — Francisite leaves light green, Chalcomenite leaves pale blue.
How to tell apart: Francisite is noticeably harder (Mohs 3.5 vs. 2.5); streak differs — Francisite leaves light green, Penfieldite leaves white; luster reads vitreous on Francisite and adamantine on Penfieldite.
Often found alongside francisite
Minerals reported to co-occur with francisite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₃Bi(SeO₃)₂O₂Cl
- Mohs hardness
- 3.5
- Density
- 5.3 g/cm³
- Colors
- Streak
- Light Green
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Platy Crystals, Crusts
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Hydrothermal Selenium-rich Deposits
- Typical price
- $100-500 for small specimen
Where rockhounds find francisite
Classic worldwide localities
- Centenario Mine, Bolivia
Field-hunting tip
Look in oxidized hydrothermal selenium-rich deposits country — that is the host setting where francisite typically forms. If you start seeing chalcomenite, penfieldite, hematite in float, you are in the right ground. Field specimens usually show a platy crystals, crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find francisite on the map
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