Thénardite is a water-soluble sulfate mineral that typically forms as a dehydration product of mirabilite in arid climates. Collectors should note that it is highly sensitive to humidity and should be stored in a sealed container to prevent it from altering or crumbling.
Is this thénardite?
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 thénardite with a known reference. Thénardite 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. Thénardite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Thénardite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white, gray, brownish, yellowish.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: tabular crystals, pyramidal, or massive encrustations.
Often confused with
Thénardite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside thénardite
Minerals reported to co-occur with thénardite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₂SO₄
- Mohs hardness
- 2.5-3
- Density
- 2.66 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Tabular Crystals, Pyramidal, Or Massive Encrustations
- Cleavage
- Distinct On {001}
- Rarity
- Common
- Uses
- Collector
- Host rock
- Evaporite Deposits in Arid Salt Lakes or Volcanic Fumaroles
- Typical price
- $10-50 per specimen
Where rockhounds find thénardite
5 mapped spotsClassic worldwide localities
- Searles Lake, California
- Laguna Salinas, Chile
- Madrid, Spain
- Great Salt Lake, Utah
- Vesuvius, Italy
Field-hunting tip
Look in evaporite deposits in arid salt lakes or volcanic fumaroles country — that is the host setting where thénardite typically forms. If you start seeing mirabilite, halite, glauberite in float, you are in the right ground. Field specimens usually show a tabular crystals, pyramidal, or massive encrustations habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Utah, North Dakota — start trip planning there.
Common questions
How do you identify thénardite?+
Where is thénardite found?+
Can I find thénardite in the United States?+
How much is thénardite worth?+
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Find thénardite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
