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Comb plessite |
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| Meteorite - Carbo, IID Iron |
| Plesssite is a fine-grained mix of kamacite
and taenite. It can also contain particles of schreibersite and
tetrataenite. It is not a simple mineral but a complex descriptive term for the various physical fields that often develop between kamacite and taenite lamellae. This composition is a two-phase mixture of the two that is the last to develop from retained taenite during primary cooling. Plessite fields, often a striking visual association, are usually framed by a continuous taenite rim. Large plessitic fields are often developed as comb plessites and result from exceedingly slow continuous primary cooling. The meteorite in the image below is Carbo, a IID iron. The primary cooling rate for Carbo is believed to have been 10°- 20° C per million years. Plessitic fields are considered secondary structures. Note the structural resemblance to the teeth of a comb and the field alignment to the host Widmanstatten pattern. |
| Figure 1. Scale bar 900 µm. |
| Comb plessite, Carbo, Iron, IID. |
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