Kollerite is a rare iron hydroxide. It was approved as a distinct mineral species in 2019. It was first described from the Poudrette Quarry, Mont Saint-Hilaire, La Vallée-du-Richelieu, Montérégie, Québec, Canada.
Is this kollerite?
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 kollerite with a known reference. Kollerite sits at Mohs 2-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Kollerite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Kollerite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, pale yellow.
- 5Look at form & habitCrystal system: triclinic. Typical habit: acicular crystals, efflorescent crusts.
Often confused with
Kollerite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Kollerite leaves white, Pharmacosiderite leaves yellowish green; luster reads vitreous on Kollerite and adamantine on Pharmacosiderite.
How to tell apart: Luster reads vitreous on Kollerite and vitreous to subadamantine on Scorodite.
Often found alongside kollerite
Minerals reported to co-occur with kollerite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (NH₄)₂Fe³⁺(SO₃)₂(OH)·H₂O
- Mohs hardness
- 2-3
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Triclinic
- Crystal habit
- Acicular Crystals, Efflorescent Crusts
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Zones of Arsenic-rich Hydrothermal Deposits
Where rockhounds find kollerite
Classic worldwide localities
- Poudrette Quarry, Québec, Canada
Field-hunting tip
Look in oxidized zones of arsenic-rich hydrothermal deposits country, the host setting where kollerite typically forms. If you start seeing arsenopyrite, goethite, gypsum in float, you are in the right ground. Field specimens usually show a acicular crystals, efflorescent crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify kollerite?+
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Find kollerite on the map
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