Meteorite San Juan 090 – Chile
Typ: iron meteorite / IIE
Locality: Antofagasta, Chile
Weight: 21,7g
Dimensions: 72 x 33 x 2 mm
Year found: 2015
Total known weight: 2,54 kg
Surface treatment: cut, polished slice (etched with acid on one side only – visible Widmanstätten patterns; the other side is polished without etching)
| Category: | San Juan 090 |
|---|---|
| By name: | San Juan 090 |
| ? Type: | Iron |
| ? Surface treatment: | Cut |
| Packaging: | None |
| Specialties: | Widmanstätten's patterns |
The San Juan 090 meteorite is an iron meteorite found on 3 February 2015 in the Antofagasta region of Chile. It is classified as a Group IIE iron meteorite and its mass is 2.54 kilograms.
The San Juan area in the Atacama Desert is one of the most important meteorite sites in the arid desert regions. Meteorites found in this area are characterised by a wide range of terrestrial ages, ranging from recent impact to more than 40,000 years, as well as limited weathering due to the extremely dry climate.
After etching, the meteorite is seen to have a polycrystalline structure, composed of small grains (0.1 to 3 mm) of kamacite, often with Neumann bands, as well as containing troilite, schreibersite and inclusions of silicates such as olivine or pyroxene.
Neumann bands
Neumann bands are fine parallel lines visible in some iron meteorites, especially those containing kamacite (a low-nickel iron-nickel alloy). These bands are caused by the deformation of the material during the extremely strong impacts the meteorite experienced during its journey through space or when it hit the Earth.
They are the result of shock transformation of the kamacite, which means that they are formed at high pressure during collision events, meaning that when a meteorite suffers a strong impact, changes occur in its internal structure, especially in the kamacite, where these thin deformations form.
Neumann bands can be observed on the etched surface of an iron meteorite, usually using nitric acid. Unlike Widmanstätten patterns, which are formed by slow cooling and have the texture of larger crystals, Neumann bands are finer and reflect the shock history of the meteorite.