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, 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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