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 ~3, 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, greenish, yellowish, grayish, or brownish.
- 5Look at form & habitCrystal system: hexagonal. 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
- ~3
- Density
- 2.72 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Hexagonal
- Crystal habit
- Pseudomorphs after thenardite, crusts, massive
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A sublimate at active volcanic fumaroles
Where rockhounds find metathénardite
Classic worldwide localities
- Glavnaya Tenoritovaya, Arsenarnaya, and Yadovitaya fumaroles, Second scoria cone, Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik Volcano, Kamchatka, Russia
Field-hunting tip
Where it forms: A sublimate at active volcanic fumaroles. If you start seeing hematite, tenorite, fluorophlogopite in float, you are in the right ground. Typical habit: pseudomorphs after thenardite, crusts, massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify metathénardite?+
Where is metathénardite found?+
What rocks look like metathénardite?+
What minerals are found with metathénardite?+
What kind of rock does metathénardite form in?+
What is metathénardite used for?+
Find metathénardite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
