Polyhalite is a complex evaporite mineral found primarily in marine sedimentary deposits. It is often identified by its characteristic brick-red to pinkish color caused by iron oxide inclusions and its occurrence in massive, granular, or fibrous aggregates within salt beds.
Is this polyhalite?
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 polyhalite with a known reference. Polyhalite sits at Mohs 2.5-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Polyhalite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Polyhalite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white, gray, yellow, red, brick-red.
- 5Look at form & habitCrystal system: triclinic. Typical habit: tabular crystals, massive, granular, fibrous.
Often confused with
Polyhalite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside polyhalite
Minerals reported to co-occur with polyhalite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K₂Ca₂Mg(SO₄)₄·2H₂O
- Mohs hardness
- 2.5-3
- Density
- 2.78 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Triclinic
- Crystal habit
- Tabular Crystals, Massive, Granular, Fibrous
- Cleavage
- Distinct On {001}
- Rarity
- Common
- Uses
- Industrial, Fertilizer, Collector
- Host rock
- Evaporite Sedimentary Sequences
- Typical price
- $10-50 for typical specimens
Where rockhounds find polyhalite
3 mapped spotsClassic worldwide localities
- Hallstatt, Austria
- Stassfurt, Germany
- Carlsbad, New Mexico, USA
- Bolshoy Severn, Russia
Field-hunting tip
Look in evaporite sedimentary sequences country, the host setting where polyhalite typically forms. If you start seeing halite, sylvite, kieserite in float, you are in the right ground. Field specimens usually show a tabular crystals, massive, granular, fibrous habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Utah, Nevada. Start trip planning there.
Common questions
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Find polyhalite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
