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Degenerate Plessite |
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| Meteorite: Henbury, IIIAB, iron. Ni 7.41% |
| Figure 1. Scale bar 1.4 mm. |
| Meteorite: Henbury, IIIAB, iron. Ni 7.41% |
| Degenerate plessite (center) is a
specific type of plessitic field found in meteorites. It's a fine-grained
mixture of kamacite (low-nickel iron) and taenite (high-nickel iron).
When these minerals cool and solidify in a disordered manner, degenerate plessite can form, leading to the irregular patterns observed. The nickel content in the plessite can influence the structure, but the primary factor is the meteorite's cooling history. Unlike other types of plessite, which may have more organized or distinct patterns, degenerate plessite lacks a clear, defined structure and is often chaotic. Any of the labeled or named plessitic fields - comb, net, cellular, etc., may be degenerate, meaning they are imperfectly developed in their formation. This is often seen in low nickel (bulk value around 7%) irons where the taenite has disappeared after full primary cooling. (1) Degenerate plessite is a secondary structure that appears incomplete in its formation. Microscopically, one can see how the plessite field is forming, but it doesn't quite finish or get there. |
| (1) Buchwald, 1975, Handbook of Iron Meteorites. |
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