Bismutoferrite is an uncommon bismuth-iron silicate that typically forms as a fine-grained, earthy or massive material in hydrothermal deposits. It is best identified by its distinct yellowish-green to olive-green color and its association with other bismuth secondary minerals. It is primarily sought by advanced collectors of bismuth-bearing species.
Is this bismutoferrite?
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 bismutoferrite with a known reference. Bismutoferrite sits at Mohs 6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: light green.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine to resinous.
- 4Match the color rangeCompare against the expected color range: green, light yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: massive.
Often confused with
Bismutoferrite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Bismutoferrite is noticeably harder (Mohs 6 vs. 3-4); streak differs, so Bismutoferrite leaves light green, Mixite leaves pale bluish green; luster reads adamantine to resinous on Bismutoferrite and vitreous, silky in aggregates on Mixite.
How to tell apart: Bismutoferrite is noticeably harder (Mohs 6 vs. ~2-4); streak differs, so Bismutoferrite leaves light green, Chrysocolla leaves white when pure; luster reads adamantine to resinous on Bismutoferrite and vitreous, porcelaneous, earthy on Chrysocolla.
How to tell apart: Bismutoferrite is noticeably harder (Mohs 6 vs. 2.5-3.5); streak differs, so Bismutoferrite leaves light green, Bismutite leaves gray; luster reads adamantine to resinous on Bismutoferrite and vitreous, waxy, may be dull to earthy on Bismutite.
Often found alongside bismutoferrite
Minerals reported to co-occur with bismutoferrite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe₂Bi(SiO₄)₂(OH)
- Mohs hardness
- 6
- Density
- 4.47 g/cm³
- Colors
- Streak
- Light green
- Luster
- Adamantine to resinous
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Massive
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Probably of hydrothermal origin, in veins cutting shale (Schneeberg, Germany)
Where rockhounds find bismutoferrite
Classic worldwide localities
- Lodi # 4 claim, Plumas Co., California, and in the Organ Mountains, Dona Ana Co., New Mexico, USA
- Schneeberg, Johanngeorgenstadt, and Gersdorf, Saxony, Germany
- Smrkovec, Slavkovský Les Mountains, about 10 km north-northeast of Mariánské Lázně, Czech Republic
- South Terras mine, St. Stephen-in-Brannel, and the Hingston Down quarry, Calstock, Cornwall, and at Buckbarrow Beck, Carney Fell, Cumbria, England
Field-hunting tip
Where it forms: Probably of hydrothermal origin, in veins cutting shale (Schneeberg, Germany). If you start seeing quartz, chalcedony, bismuth in float, you are in the right ground. Typical habit: massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify bismutoferrite?+
Where is bismutoferrite found?+
Is bismutoferrite safe to handle?+
What rocks look like bismutoferrite?+
What minerals are found with bismutoferrite?+
What kind of rock does bismutoferrite form in?+
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Find bismutoferrite on the map
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