Hilarionite is a very rare iron sulfate mineral typically found as earthy, pale green coatings in oxidized ore zones. It was first described from the historic mines of the Laurion district in Greece. Collectors prize it for its unique chemical composition and restricted locality occurrences.
Is this hilarionite?
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 hilarionite with a known reference. Hilarionite 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. Hilarionite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Hilarionite typically shows a dull luster.
- 4Match the color rangeCompare against the expected color range: light green, yellowish-green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: crusts, aggregates, earthy.
Often confused with
Hilarionite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Hilarionite leaves white, Jarosite leaves yellow; luster reads dull on Hilarionite and vitreous on Jarosite.
How to tell apart: Streak differs — Hilarionite leaves white, Copiapite leaves yellow; luster reads dull on Hilarionite and pearly on Copiapite.
How to tell apart: Luster reads dull on Hilarionite and vitreous on Melanterite.
Often found alongside hilarionite
Minerals reported to co-occur with hilarionite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe₃(SO₄)₂(OH)₅·6H₂O
- Mohs hardness
- 2-3
- Density
- 2.68 g/cm³
- Streak
- White
- Luster
- Dull
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Crusts, Aggregates, Earthy
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Hydrothermal Sulfide Deposits
- Typical price
- $50-300 per specimen
Where rockhounds find hilarionite
Classic worldwide localities
- Hilarion Mine, Greece
- Laurion mining district, Greece
Field-hunting tip
Look in oxidized hydrothermal sulfide deposits country — that is the host setting where hilarionite typically forms. If you start seeing goethite, gypsum, jarosite in float, you are in the right ground. Field specimens usually show a crusts, aggregates, earthy habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find hilarionite on the map
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