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Net plessite |
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| Meteorite - Cape York, IIIAB Iron |
| Figure 1. Scale bar 500 µm. |
| Meteorite - Cape York, IIIAB Iron |
| Net plessite, Cape York. |
| Net plessite is a secondary
structure in iron meteorites. It forms through a complex cooling process after
the initial solidification of the meteorite. The meteorite’s metal is initially in a high-temperature phase called taenite (high Ni content) - a face-centered cubic (FCC) structure. As the meteorite cools, taenite begins to transform into kamacite (lower Ni content) - a body-centered cubic (BCC) structure. This transformation occurs through a series of intermediate phases and reactions. Martensite plays a crucial role in the formation of net plessite in iron meteorites. During cooling, martensite (a supersaturated solid solution of carbon in iron) forms. This transformation occurs below the martensite start temperature (Ms) and is a diffusionless process that occurs rapidly. The martensite then decomposes into a fine-grained mixture of kamacite and taenite, known as plessite. It develops in the retained taenite regions referred to as “fields,” creating a net-like appearance. Net plessite fields form in the gaps between the larger lamellae of kamacite and taenite, creating a net-like texture. |
| Figure 2. Scale bar 300 µm. |
| Meteorite - Cape york, IIIAB Iron |
| Net plessite, Cape York. |
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