What Actually Causes Aletai Meteorite to Rust: The Chemistry of “Lawrencite Disease”

Aletai meteorite rusts when chloride and moisture reach the iron — a process collectors call "lawrencite disease." But the usual explanation for it is out of date. The chloride is not a cosmic mineral the meteorite carried from space; it is picked up on Earth, and the corrosion is driven by an iron oxyhydroxide called akaganéite. The distinction sounds academic, but it is the difference between repeating a myth and actually understanding how to keep a piece stable.

Where the name "lawrencite" comes from

For more than a century, the green-to-brown weeping seen on iron meteorites was blamed on lawrencite — iron(II) chloride, FeCl₂ — assumed to be a primary mineral that formed in space and "switched on" when the meteorite met humid air. The condition is still widely called "lawrencite disease," and as a name it is useful shorthand. The mechanism it implies, however, has not survived closer study.

What modern conservation science found

The picture was corrected by Buchwald and Clarke (1989), who examined iron meteorites recovered from the pristine, dry environment of Antarctica alongside heavily weathered desert finds. They showed that the chloride driving the corrosion is largely terrestrial — drawn into the metal from soil, humidity, and handling after the meteorite landed — rather than a cosmic mineral carried from space. The destructive phase is not stable lawrencite but akaganéite (β-FeOOH), a chloride-bearing iron oxyhydroxide. More recent crystallography has identified transient hydroxychlorides such as parahibbingite at the metal–rust interface — the unstable phases that earlier observers had been calling "lawrencite."

In Aletai specifically — an iron classified Iron, IIIE-an (anomalous) — chloride concentrates along the internal boundaries of the metal: the edges between the kamacite and taenite phases, and the margins of inclusions such as schreibersite and troilite. Those boundaries are where the trouble starts.

The cycle that makes it persistent

Here is the part that matters for care. Chloride gathered at these boundaries pulls in atmospheric moisture and forms a small, acidic, highly corrosive solution. As iron dissolves, akaganéite precipitates — and akaganéite is hygroscopic and holds chloride within its structure. As humidity rises and falls, it releases that chloride again to attack fresh metal, then re-forms. The chloride is not used up; it cycles.

That is why this corrosion is self-sustaining, and why it appears to push outward from inside the piece rather than sitting on the surface like ordinary rust. It does not need a fresh supply of chloride from outside — it recycles what is already there, as long as moisture is available.

What this means for caring for Aletai

The science changes the explanation, not the routine. The whole goal is to deny that cycle the moisture it needs:

• Keep the piece dry. Avoid showering, swimming, and prolonged humidity.
• Clean with 99% isopropyl alcohol, not water — water feeds the very reaction you are trying to stop.
• Seal with Renaissance Wax, the microcrystalline wax used by the British Museum Research Laboratory and major collections. It is breathable and reversible, and does not trap moisture against the metal the way a hard resin coating can.

For the broader question of whether and how meteorite jewelry rusts, see does meteorite jewelry rust; for the full routine, see Materials & Care.

None of this is a defect unique to Aletai. It is how iron meteorites behave once they reach Earth’s humid, oxygen-rich air, and it is manageable. Movalor documents the material honestly rather than hiding how it behaves — because a piece you understand is a piece you can keep.

Frequently Asked Questions

What actually causes Aletai meteorite to rust?

Chloride and moisture reaching the iron. The chloride is largely terrestrial — absorbed after the meteorite landed — and the active corrosion is driven by the iron oxyhydroxide akaganéite. The condition is traditionally called "lawrencite disease," though modern research attributes it to chloride and akaganéite rather than to surviving cosmic lawrencite.

Is "lawrencite disease" an accurate term?

It is the traditional name and still widely used, but the mechanism it implies is outdated. Studies of pristine meteorites (Buchwald & Clarke, 1989) showed the chloride is largely terrestrial and the destructive phase is akaganéite, not stable cosmic lawrencite (FeCl₂).

Why does the rust seem to come from inside the piece?

Chloride concentrates along internal phase and inclusion boundaries and forms an acidic solution there. Akaganéite holds and re-releases the chloride as humidity changes, so the reaction sustains itself and works outward from within rather than sitting on the surface.

How do you stop Aletai meteorite from rusting?

Keep it dry, clean it with 99% isopropyl alcohol rather than water, and seal it with Renaissance Wax. The aim is to deny the corrosion cycle the moisture it needs; the wax is breathable and reversible, unlike hard resin coatings.