Césarferreiraite is a rare hydrated iron arsenate mineral typically found as small, yellow, prismatic crystals in oxidized zones of arsenic-bearing pegmatites. It is often discovered as radial clusters associated with other secondary arsenic minerals like scorodite. Collectors should handle it with care due to its arsenic content.
Is this césarferreiraite?
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 césarferreiraite with a known reference. Césarferreiraite 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. Streak: pale to greenish yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: pale, greenish yellow.
- 5Look at form & habitCrystal system: triclinic. Typical habit: prismatic crystals, radial aggregates.
Often confused with
Césarferreiraite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Scorodite is the harder of the two (Mohs 3.5-4 vs. 2); streak differs, so Césarferreiraite leaves pale to greenish yellow, Scorodite leaves greenish white.
How to tell apart: Streak differs, so Césarferreiraite leaves pale to greenish yellow, Pharmacosiderite leaves yellowish green; luster reads vitreous on Césarferreiraite and adamantine to greasy on Pharmacosiderite.
Often found alongside césarferreiraite
Minerals reported to co-occur with césarferreiraite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- FeFe₂(AsO₄)₂(OH)₂·8H₂O
- Mohs hardness
- 2
- Density
- 2.934 g/cm³
- Colors
- PaleGreenish yellow
- Streak
- Pale to greenish yellow
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Triclinic
- Crystal habit
- Prismatic crystals, radial aggregates
- Cleavage
- Distinct on {010} and {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Filling a miarolitic cavity in a zoned granitic pegmatite, likely replacing arsenopyrite
Where rockhounds find césarferreiraite
Classic worldwide localities
- Eduardo pegmatite mine, near Boa Vista creek, Conselheiro Pena municipality, Minas Gerais, Brazil
Field-hunting tip
Where it forms: Filling a miarolitic cavity in a zoned granitic pegmatite, likely replacing arsenopyrite. If you start seeing pharmacosiderite, scorodite, arsenopyrite in float, you are in the right ground. Typical habit: prismatic crystals, radial aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
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Find césarferreiraite on the map
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