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. Streak: bluish white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous, pearly on cleavages.
- 4Match the color rangeCompare against the expected color range: blue.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: encrustations.
Often confused with
Ransomite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Ransomite leaves bluish white, Chalcanthite leaves white.
How to tell apart: Brochantite is the harder of the two (Mohs 3.5-4 vs. 2.5); streak differs, so Ransomite leaves bluish white, Brochantite leaves pale green.
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
- CuFe₂(SO₄)₄(H₂O)₃
- Mohs hardness
- 2.5
- Density
- 2.632 g/cm³
- Colors
- Streak
- Bluish white
- Luster
- Vitreous, pearly on cleavages
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Encrustations
- Cleavage
- On {001}, perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Very rare, formed as the result of a mine fire (United Verde mine, Arizona, USA); coating oxidizing copper-bearing pyrite (Campbell shaft, Arizona, USA)
Where rockhounds find ransomite
Classic worldwide localities
- United Verde mine, Jerome, Yavapai Co., and in the Campbell shaft, Bisbee, Cochise Co, Arizona, USA
Field-hunting tip
Where it forms: Very rare, formed as the result of a mine fire (United Verde mine, Arizona, USA); coating oxidizing copper-bearing pyrite (Campbell shaft, Arizona, USA). If you start seeing pyrite, voltaite, römerite in float, you are in the right ground. Typical habit: encrustations. 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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