Pickeringite is a secondary sulfate mineral typically found as efflorescent, fibrous, or needle-like growths in arid environments or mine tailings. Collectors should look for delicate white to pale pink crusts forming in dry, oxidized zones of sulfide ore bodies.
Is this pickeringite?
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 pickeringite with a known reference. Pickeringite sits at Mohs 1.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: colorless, yellowish white, reddish white, greenish white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: encrustations, fibrous, reniform.
Often confused with
Pickeringite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside pickeringite
Minerals reported to co-occur with pickeringite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- MgAl₂(SO₄)₄·22H₂O
- Mohs hardness
- 1.5
- Density
- 1.73-1.79 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Encrustations, fibrous, reniform
- Cleavage
- Poor on {010}
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- A common secondary mineral formed by alteration of pyrite in aluminous rocks or in coal seams; in the oxidized zone of pyritic hydrothermal mineral deposits, typically in arid regions, typically post-mining
Where rockhounds find pickeringite
1 mapped spotsClassic worldwide localities
- Tucumcari, Quay Co., New Mexico, USA
- Geysers, Sonoma Co., California, USA
- Alum Point, Salt Lake Co., Utah, USA
- Cerros Pintados, 80 km southeast of Iquique, Tarapacá, Chile
- Quetena, west of Calama, and Chuquicamata, Antofagasta, Chile
- Newport, Nova Scotia, and from the junction of the two main branches of the Smoky River, Alberta, Canada
Field-hunting tip
Where it forms: A common secondary mineral formed by alteration of pyrite in aluminous rocks or in coal seams; in the oxidized zone of pyritic hydrothermal mineral deposits, typically in arid regions, typically post-mining. If you start seeing kalinite, alunogen, epsomite in float, you are in the right ground. Typical habit: encrustations, fibrous, reniform. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Missouri. Start trip planning there.
Common questions
How do you identify pickeringite?+
Where is pickeringite found?+
Can I find pickeringite in the United States?+
What rocks look like pickeringite?+
What minerals are found with pickeringite?+
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What is pickeringite used for?+
Find pickeringite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
