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 4-4.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine.
- 4Match the color rangeCompare against the expected color range: gray, gray white.
- 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.
How to tell apart: Luster reads adamantine on Rooseveltite and resinous to adamantine on Atelestite.
How to tell apart: Streak differs, so Rooseveltite leaves white, Mixite leaves pale bluish green; luster reads adamantine on Rooseveltite and vitreous, silky in aggregates on Mixite.
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
- 4-4.5
- Density
- 6.86-7.01 g/cm³
- Colors
- Streak
- White
- Luster
- Adamantine
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Acicular or fibrous crystals, often as crusts or aggregates
- Cleavage
- Good
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Vey rare in cassiterite veinlets in rhyolite-dacite lava flows (Santiaguillo, Bolivia); in the oxidized zone of a breccia pipe (San Francisco de los Andes, Argentina)
Where rockhounds find rooseveltite
Classic worldwide localities
- Santiaguillo, west of Maragua, POtOSI, Bolivia
- San Francisco de los Andes and Cerro Negro de la Aguadita mines, San Juan Province, Argentina
- Moldava, about 20 km northwest of Teplice, Czech Republic
- Odsbach Valley, near Oberkirch, at the Clara mine, near Oberwolfach, and on the Schmiedestollen dump, Black Forest, Germany
- An undefined locality in the Chatkal Mountains, Uzbekistan
Field-hunting tip
Where it forms: Vey rare in cassiterite veinlets in rhyolite-dacite lava flows (Santiaguillo, Bolivia); in the oxidized zone of a breccia pipe (San Francisco de los Andes, Argentina). If you start seeing cassiterite, preisingerite, bismutite in float, you are in the right ground. Typical habit: acicular or fibrous crystals, often as crusts or aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
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Find rooseveltite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
