Mohrite is a rare ammonium iron sulfate typically found as a secondary mineral in mine dumps or near volcanic fumaroles. It occurs as small, pale green prismatic crystals that are sensitive to dehydration and must be stored in closed containers to prevent weathering.
Is this mohrite?
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 mohrite with a known reference. Mohrite sits at Mohs 2-2.5, 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: vitreous.
- 4Match the color rangeCompare against the expected color range: light green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals, crusts.
Often confused with
Mohrite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside mohrite
Minerals reported to co-occur with mohrite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (NH₄)₂Fe(SO₄)₂·6H₂O
- Mohs hardness
- 2-2.5
- Density
- 1.800-1.862 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic crystals, crusts
- Cleavage
- Perfect on {102}; distinct on {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In boriferous fumaroles and geysers
Where rockhounds find mohrite
Classic worldwide localities
- Travale, near Montieri, Val di Cecina, Tuscany, Italy
Field-hunting tip
Where it forms: In boriferous fumaroles and geysers. If you start seeing copiapite, jarosite, sulfur in float, you are in the right ground. Typical habit: prismatic crystals, crusts. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify mohrite?+
Where is mohrite found?+
What rocks look like mohrite?+
What minerals are found with mohrite?+
What kind of rock does mohrite form in?+
What is mohrite used for?+
Find mohrite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
