Butlerite is a rare secondary iron sulfate mineral typically found as a dehydration product in the oxidized zones of ore deposits. It most commonly occurs as small, orange-to-yellowish tabular crystals or as efflorescent crusts formed in arid mining environments. Collectors prize it for its vibrant color, though it is fragile and sensitive to humidity.
Is this butlerite?
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 butlerite with a known reference. Butlerite 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: pale yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: orange, dark yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals or earthy to powdery crusts.
Often confused with
Butlerite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads vitreous on Butlerite and subadamantine to vitreous, resinous on fractures on Jarosite.
How to tell apart: Luster reads vitreous on Butlerite and pearly on {010} on Copiapite.
How to tell apart: Streak differs, so Butlerite leaves pale yellow, Fibroferrite leaves white; luster reads vitreous on Butlerite and pearly, silky in aggregates on Fibroferrite.
Often found alongside butlerite
Minerals reported to co-occur with butlerite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe³⁺(SO₄)(OH)·2H₂O
- Mohs hardness
- 2.5
- Density
- 2.55 g/cm³
- Colors
- OrangeDark yellow
- Streak
- Pale yellow
- Luster
- Vitreous
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular crystals or earthy to powdery crusts
- Cleavage
- On {100}, perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Rarely formed from the oxidation of pyritic ore; may be formed under fumarolic conditions from mine fires
Where rockhounds find butlerite
Classic worldwide localities
- United Verde copper mine, Jerome, Yavapai Co., Arizona, USA
- Lone Star mine, La Bajada district, Santa Fe Co., New Mexico, USA
- Dexter No. 7 mine, Calf Mesa, San Rafael district, Emery Co., Utah, USA
- Cimarron, Gunnison Co., Colorado, USA
- Santa Elena mine, Quebrada de La Alcaparrosa, San Juan Province, Argentina
- Chuquicamata and Quetena, west of Calama, Antofagasta, Chile
Field-hunting tip
Where it forms: Rarely formed from the oxidation of pyritic ore; may be formed under fumarolic conditions from mine fires. If you start seeing parabutlerite, copiapite, fibroferrite in float, you are in the right ground. Typical habit: tabular crystals or earthy to powdery crusts. Train your eye for that shape before scanning the outcrop.
Common questions
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Find butlerite on the map
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