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 — that is 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
How do you identify polyhalite?+
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Find polyhalite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
