Muonionalusta Iron Meteorite Slice, IVA Fine Octahedrite, 330.81g, Etched Widmanstätten Pattern

Geometric crystalline structure across 330.81 grams

This Muonionalusta slice weighs 330.81g and delivers clear visibility into the interlocking kamacite and taenite lamellae that define the IVA fine octahedrite structure. The etched surface reveals angular crystal boundaries and the geometric precision that results from millions of years of controlled cooling inside a differentiated asteroid. The pattern extends across the full face of the slice without significant interruption, offering both visual clarity and structural continuity.

The slice format provides direct access to the cross-section of the metallic body. Etching enhances the contrast between nickel-poor kamacite and nickel-rich taenite, making the Widmanstätten pattern visible under normal lighting. At this weight, the specimen balances display scale with structural detail, showing how kamacite plates intersect at consistent angles determined by the cubic crystal lattice of the parent metal.

Widmanstätten pattern and octahedrite classification

The Widmanstätten pattern forms when molten nickel-iron alloy cools at rates between one and several hundred degrees Celsius per million years. Under these conditions, kamacite nucleates along the octahedral planes of the taenite crystal structure, creating parallel bands that intersect at 60- and 120-degree angles. This geometry is visible across the etched surface of this slice and reflects the internal symmetry of the original metallic crystal.

IVA fine octahedrites contain kamacite bandwidth between 0.2 and 0.5 millimeters, a range that produces tight, visually dense patterning. The fine classification distinguishes Muonionalusta from coarser octahedrites and marks it as material that cooled slowly enough to allow crystal separation but quickly enough to prevent the formation of wider kamacite plates. Etching with acid removes material selectively, deepening the pattern and amplifying the contrast between crystal phases.

Scientific context

Muonionalusta originates from the core of a differentiated asteroid that separated into layers of silicate mantle and metallic interior during the first few million years of solar system history. Collisional disruption exposed this core material and sent fragments into orbital trajectories that eventually intersected Earth. The meteorite's IVA classification places it within a group of iron meteorites that share chemical and structural similarities, indicating a common parent body.

The slow cooling rate preserved in the Widmanstätten pattern indicates that the parent body remained intact and insulated for millions of years after initial solidification. This cooling history allows researchers to model the thermal evolution of early planetary cores and understand how metal segregates under low-gravity conditions. For context on how these processes relate to meteorite formation broadly, see Learn About Meteorites.

Frequently asked questions

Is this meteorite authenticated? Muonionalusta is classified as an IVA fine octahedrite in the Meteoritical Bulletin. You can verify this classification through the Meteoritical Bulletin database. This specimen includes a certificate of authenticity documenting its classification, weight, and provenance.

What is a fine octahedrite? Fine octahedrite refers to the bandwidth of kamacite lamellae in the Widmanstätten pattern. In IVA fine octahedrites like Muonionalusta, kamacite plates measure between 0.2 and 0.5 millimeters in width. This produces a tightly spaced, geometrically dense pattern that distinguishes fine octahedrites from medium and coarse varieties.

What is included with this specimen? This listing includes the 330.81g Muonionalusta slice and a certificate of authenticity. No display stand is included unless explicitly stated in the product variant description.

How was the Widmanstätten pattern revealed? The slice was cut from the meteorite mass, polished to a flat surface, and then etched with a mild acid solution. The acid differentially removes kamacite faster than taenite, creating depth contrast that makes the crystal structure visible. This process does not alter the meteorite's composition or authenticity.

Where was Muonionalusta found? Muonionalusta was recovered in Norrbotten County, Sweden, in 1906. It is a witnessed find with documented recovery history and remains one of the most widely recognized iron meteorites from Scandinavia.

Display and collector value

Muonionalusta holds consistent demand among collectors due to its visual clarity, well-documented classification, and the accessibility of its structural features. The etched Widmanstätten pattern provides immediate confirmation of extraterrestrial origin and demonstrates the slow-cooling conditions that characterized early asteroid cores. At 330.81g, this slice offers substantial mass without requiring specialized mounting or storage.

The specimen works well in collections focused on iron meteorites, asteroid-derived material, or geological processes visible at the macroscopic scale. The pattern remains stable after etching and does not require re-treatment under normal indoor conditions. For additional classified iron meteorite specimens with etched structures, explore our Iron Meteorites collection.

Meteoritical Bulletin entry: Muonionalusta | Classification: Iron meteorite (IVA fine octahedrite) | Find, Sweden, 1906