Ransomite is an extremely rare hydrous iron copper sulfate that typically forms as delicate, pale blue acicular crystal aggregates. It is an oxidation product found in mine workings, often appearing as ephemeral crusts or thin coatings that require careful storage away from humidity. It is best identified through its specific association with other sulfate minerals in copper-rich deposits.
Is this ransomite?
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 ransomite with a known reference. Ransomite sits at Mohs 2.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Ransomite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Ransomite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: blue, pale blue.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: acicular crystals, fibrous, efflorescent crusts.
Often confused with
Ransomite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside ransomite
Minerals reported to co-occur with ransomite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- FeCu₂(SO₄)₃·6H₂O
- Mohs hardness
- 2.5
- Density
- 2.44 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Acicular Crystals, Fibrous, Efflorescent Crusts
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Zones of Copper-rich Sulfide Ore Deposits
- Typical price
- $50-300 per specimen
Where rockhounds find ransomite
Classic worldwide localities
- United Verde Mine, Jerome, Arizona, USA
Field-hunting tip
Look in oxidized zones of copper-rich sulfide ore deposits country — that is the host setting where ransomite typically forms. If you start seeing chalcanthite, coquimbite, copiapite in float, you are in the right ground. Field specimens usually show a acicular crystals, fibrous, efflorescent crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find ransomite on the map
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