Mandarinoite is a rare hydrated iron selenite mineral that typically forms as delicate, transparent, yellow-green blades or crusts. It is most often found in association with other selenium minerals in oxidized zones of hydrothermal deposits. Because of its rarity and sensitivity to atmospheric conditions, it is highly sought after by advanced systematic mineral collectors.
Is this mandarinoite?
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 mandarinoite with a known reference. Mandarinoite sits at Mohs ~2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: very pale green.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to slightly greasy.
- 4Match the color rangeCompare against the expected color range: greenish white, light green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: encrustations, reniform, stalactitic.
Often confused with
Mandarinoite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Mandarinoite leaves very pale green, Jarosite leaves pale yellow; luster reads vitreous to slightly greasy on Mandarinoite and subadamantine to vitreous, resinous on fractures on Jarosite.
How to tell apart: Streak differs, so Mandarinoite leaves very pale green, Coquimbite leaves white.
Often found alongside mandarinoite
Minerals reported to co-occur with mandarinoite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe₂Se₃O₉·6H₂O
- Mohs hardness
- ~2.5
- Density
- 2.93 g/cm³
- Streak
- Very pale green
- Luster
- Vitreous to slightly greasy
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Encrustations, reniform, stalactitic
- Cleavage
- Probable parting on {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Probably formed by the simultaneous oxidation of penroseite and pyrite in a selenium-rich ore deposit (Pacajake mine, Bolivia)
Where rockhounds find mandarinoite
Classic worldwide localities
- De Lamar mine, Silver City, Owyhee Co., Idaho, USA
- Gold Quarry mine, near Carlin, Maggie Creek district, Eureka Co., and as Wind Mountain mine, San Emidio district, Washoe Co., Nevada, USA
- Darwin, Inyo Co., California, USA
- Pacajake mine, Hiaco, 30 km east-northeast of Colquechaca, and at the El Dragón mine, 30 km southwest of Cerro Rico de Potosí, Potosí, Bolivia
- El Plomo mine, Ojojona district, Tegucigalpa, Honduras
- Skouriotissa mine, Cyprus
Field-hunting tip
Where it forms: Probably formed by the simultaneous oxidation of penroseite and pyrite in a selenium-rich ore deposit (Pacajake mine, Bolivia). If you start seeing penroseite, siderite, goethite in float, you are in the right ground. Typical habit: encrustations, reniform, stalactitic. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify mandarinoite?+
Where is mandarinoite found?+
Is mandarinoite safe to handle?+
What rocks look like mandarinoite?+
What minerals are found with mandarinoite?+
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Find mandarinoite on the map
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