Kremersite is a rare ammonium iron chloride mineral typically found as a volcanic sublimate in active fumaroles. It forms bright red octahedral crystals or crusts that are highly sensitive to moisture and must be stored in a dry, sealed environment to prevent decomposition.
Is this kremersite?
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 kremersite with a known reference. Kremersite sits at Mohs 2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: yellowish.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: red, brown red, orange.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: pseudo octohedral, water soluble.
Often confused with
Kremersite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside kremersite
Minerals reported to co-occur with kremersite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (NH₄)₂FeCl₅·H₂O
- Mohs hardness
- 2
- Density
- 2.175 g/cm³
- Streak
- Yellowish
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Pseudo octohedral, water soluble
- Cleavage
- Perfect on {211} and {011}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- As sublimates around fumaroles
Where rockhounds find kremersite
Classic worldwide localities
- Vesuvius, Campania, Italy
- Kliuchevsky volcano, Kamchatka Peninsula, and at Kopeysk, Chelyabinsk coal basin, Southern Ural Mountains, Russia
Field-hunting tip
Where it forms: As sublimates around fumaroles. If you start seeing erythrosiderite, molysite, hematite in float, you are in the right ground. Typical habit: pseudo octohedral, water soluble. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify kremersite?+
Where is kremersite found?+
Is kremersite safe to handle?+
What rocks look like kremersite?+
What minerals are found with kremersite?+
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Find kremersite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
