Sylvite is a primary source of potash and typically forms in salt deposits as a result of the evaporation of seawater. It is very similar to halite but can often be distinguished by its bitter, salty taste and its tendency to be slightly more brittle or have a different cleavage pattern when observed under magnification.
Is this sylvite?
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 sylvite with a known reference. Sylvite sits at Mohs 2, 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: white, colorless, red, orange, blue, yellowish white, reddish white, bluish white, brownish white.
- 5Look at form & habitCrystal system: cubic. Typical habit: euhedral crystals, fibrous, massive.
Often confused with
Sylvite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside sylvite
Minerals reported to co-occur with sylvite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KCl
- Mohs hardness
- 2
- Density
- 1.993 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Cubic
- Crystal habit
- Euhedral crystals, fibrous, massive
- Cleavage
- {001}, perfect
- Rarity
- Common
- Uses
- Fertilizer, Industrial, Collector
- Host rock
- In sedimentary basins, forming thick bedded deposits with halite; as a sublimate in volcanic fumaroles; in nitrate beds and cave deposits; a product of burning coal
Where rockhounds find sylvite
5 mapped spotsClassic worldwide localities
- Permian salt basin of southeastern New Mexico, in the Carlsbad potash district, Eddy Co. Potash Corporation of America mine, and adjacent parts, Texas, USA
- Vesuvius, Campania, Italy
- Hallein, Salzburg, Austria
- Westeregeln and Stassfurt, 34 km south of Magdeburg, Saxony-Anhalt, and at Bernburg, Lower Saxony, Germany
- Aislaby, near Whitby, Yorkshire, England
- Kalusz, Ukraine
Field-hunting tip
Where it forms: In sedimentary basins, forming thick bedded deposits with halite; as a sublimate in volcanic fumaroles; in nitrate beds and cave deposits; a product of burning coal. If you start seeing halite, kieserite, kainite in float, you are in the right ground. Typical habit: euhedral crystals, fibrous, massive. 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 sylvite?+
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Can I find sylvite in the United States?+
What rocks look like sylvite?+
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Find sylvite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
