Rooseveltite is a rare bismuth arsenate mineral that typically forms as a secondary product in the oxidized portions of ore deposits. It is most frequently identified by its delicate acicular or fibrous white to pale yellow clusters found encrusting other bismuth-bearing minerals.
Is this rooseveltite?
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 rooseveltite with a known reference. Rooseveltite 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. Rooseveltite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Rooseveltite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, pale yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: acicular or fibrous crystals, often as crusts or aggregates.
Often confused with
Rooseveltite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside rooseveltite
Minerals reported to co-occur with rooseveltite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Bi(AsO₄)
- Mohs hardness
- 3.5
- Density
- 5.7-6.1 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Acicular or Fibrous Crystals, Often as Crusts or Aggregates
- Cleavage
- Good
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Zones of Bismuth-rich Hydrothermal Mineral Deposits
- Typical price
- $50-300 per specimen depending on size and quality
Where rockhounds find rooseveltite
Classic worldwide localities
- San Francisco mine, Chile
- Cerro Negro, Argentina
- Black Pine mine, USA
Field-hunting tip
Look in oxidized zones of bismuth-rich hydrothermal mineral deposits country — that is the host setting where rooseveltite typically forms. If you start seeing atelestite, mixite, bismutite in float, you are in the right ground. Field specimens usually show a acicular or fibrous crystals, often as crusts or aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find rooseveltite on the map
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