Degenerate plessite, found at
the center of certain meteoritic plessitic fields, is a fine-grained, chaotic
blend of kamacite (low-nickel iron) and taenite (high-nickel iron). It forms
when these minerals cool and solidify in a disordered way, resulting in
irregular, poorly defined patterns. While nickel content plays a role in its
structure, the meteorite’s cooling history is the main driver. Unlike
other plessite varieties—such as comb, net, or cellular—which display
more organized arrangements, degenerate plessite stands out for its lack of
clear structure. This imperfection can occur in any named plessitic field,
particularly in low-nickel irons (around 7% bulk nickel), where taenite fades
after initial cooling. As a secondary feature, degenerate plessite appears
incomplete, with microscopic views revealing a formation process that starts
but never fully develops.
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