Ahlfeldite is a rare nickel-cobalt selenite mineral typically found as small, pink tabular crystals or crusts in oxidized zones of hydrothermal ore deposits. It is highly sought after by mineral collectors specializing in rare secondary species, particularly from its type locality in Bolivia.
Is this ahlfeldite?
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 ahlfeldite with a known reference. Ahlfeldite 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. Ahlfeldite leaves a pinkish-white streak.
- 3Read the lusterHold the specimen under a strong light. Ahlfeldite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: pink, reddish-pink.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals, crusts, radial aggregates.
Often confused with
Ahlfeldite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Ahlfeldite leaves pinkish-white, Cobaltomenite leaves pink.
How to tell apart: Streak differs — Ahlfeldite leaves pinkish-white, Erythrite leaves pale pink; luster reads vitreous on Ahlfeldite and adamantine to pearly on Erythrite.
Often found alongside ahlfeldite
Minerals reported to co-occur with ahlfeldite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Ni,Co)SeO₃·2H₂O
- Mohs hardness
- 2.5
- Density
- 4.26 g/cm³
- Colors
- Streak
- Pinkish-white
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular Crystals, Crusts, Radial Aggregates
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Selenium-rich Mineral Deposits
- Typical price
- $50-300 per thumbnail specimen
Where rockhounds find ahlfeldite
Classic worldwide localities
- Huanuni Mine, Bolivia
- Sierra de Cacheuta, Argentina
- Trogtal, Germany
Field-hunting tip
Look in hydrothermal selenium-rich mineral deposits country — that is the host setting where ahlfeldite typically forms. If you start seeing penroseite, clausthalite, guanajuatite in float, you are in the right ground. Field specimens usually show a tabular crystals, crusts, radial aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find ahlfeldite on the map
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