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, 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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What minerals are found with thénardite?+
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Find thénardite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
