Metahohmannite is a rare hydrated iron sulfate that typically forms in the arid, oxidized zones of pyrite-rich mineral deposits. It is often found as a dehydration product of hohmannite, manifesting as small, yellow, translucent crystals or crusts that are easily overlooked by general collectors.
Is this metahohmannite?
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 metahohmannite with a known reference. Metahohmannite sits at Mohs 2.5-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: light yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: orange.
- 5Look at form & habitCrystal system: triclinic. Typical habit: pulverulent.
Often confused with
Metahohmannite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Metahohmannite leaves light yellow, Hohmannite leaves yellow-orange.
How to tell apart: Streak differs, so Metahohmannite leaves light yellow, Amarantite leaves lemon-yellow.
How to tell apart: Streak differs, so Metahohmannite leaves light yellow, Coquimbite leaves white.
Often found alongside metahohmannite
Minerals reported to co-occur with metahohmannite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe₂O(SO₄)₂·4H₂O
- Mohs hardness
- 2.5-3
- Density
- 2.568 g/cm³
- Colors
- Streak
- Light yellow
- Luster
- Vitreous
- Transparency
- Semitransparent
- Crystal system
- Triclinic
- Crystal habit
- Pulverulent
- Cleavage
- None observed
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Formed by the partial dehydration of hohmannite
Where rockhounds find metahohmannite
Classic worldwide localities
- Redington mercury mine, Knoxville, Napa Co., California, USA
- Antofagasta, from Chuquicamata, at Quetena, west of Calama, and Alcaparrosa, near Cerritos Bayos, southwest of Calama, Chile
- Saghand, Yazd, Iran
Field-hunting tip
Where it forms: Formed by the partial dehydration of hohmannite. If you start seeing hohmannite in float, you are in the right ground. Typical habit: pulverulent. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify metahohmannite?+
Where is metahohmannite found?+
What rocks look like metahohmannite?+
What minerals are found with metahohmannite?+
What kind of rock does metahohmannite form in?+
What is metahohmannite used for?+
Find metahohmannite on the map
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