Iron, IIC, plessitic octahedrite
standby for perryville photo
Found August 1906
37° 44' N., 89° 53' W.

An angular mass of 17.5 kg was found on the farm of Patrick Monaghan about one mile west of Perryville, Missouri. The mass was sticking out of the soil as if it had been previously disturbed by plowing. It has suffered from terrestrial weathering and lost an average of 1–2 mm from the surface, but still preserves sections of the heat-affected zone and retains evidence of ablation pits.

A Ni content of ~9.6% creates a µm-sized Thomson (Widmanstätten) structure of fine-grained plessite composed of kamacite spindles having widths of ~0.06 mm and lengths up to ~0.9 mm, most all of them containing nuclei of schreibersite. Perryville began as a single taenite crystal that formed a progressively finer structure as it cooled. This uncommon plessitic structure is transitional between ataxites and finest octahedrites.

The above photo shows a 11.5 g etched partial slice that displays kamacite spindles in a µm-sized Thomson (Widmanstätten) pattern. An ~1 mm shocked troilite nodule is visible on this slice. These 0.1–2 mm nodules generally occur every 25 cm², rarely attaining a size of up to 8 mm. The photo below is from the National Museum, showing the original mass.

Perryville is closely related to the other six group IIC meteorites: Ballinoo, Cratheús [1950], Darinskoe, Kumerina, Salt River, and Unter Mässing; the previously included iron Wiley has been eliminated on the basis of its HSE values and W isotopes (Tornabene et al., 2018). To learn more about the relationship between this and other iron chemical groups, see Appendix III.

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