Metathénardite is a rare polymorph of sodium sulfate that typically forms as pseudomorphs after mirabilite. It is unstable under normal surface conditions, often reverting to thenardite or dehydrating when exposed to air. Collectors primarily find it in arid, saline evaporite basins.
Is this metathénardite?
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 metathénardite with a known reference. Metathénardite sits at Mohs 2.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Metathénardite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Metathénardite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, grayish.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: pseudomorphs after thenardite, crusts, massive.
Often confused with
Metathénardite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside metathénardite
Minerals reported to co-occur with metathénardite. 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
- Density
- 2.65 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Pseudomorphs After Thenardite, Crusts, Massive
- Cleavage
- Good On {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Evaporite Deposits
- Typical price
- $20-100 per specimen
Where rockhounds find metathénardite
Classic worldwide localities
- Spain
- United States
- Chile
- Egypt
Field-hunting tip
Look in evaporite deposits country — that is the host setting where metathénardite typically forms. If you start seeing thenardite, halite, mirabilite in float, you are in the right ground. Field specimens usually show a pseudomorphs after thenardite, crusts, massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify metathénardite?+
Where is metathénardite found?+
How much is metathénardite worth?+
What rocks look like metathénardite?+
What minerals are found with metathénardite?+
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Find metathénardite on the map
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