ST. GENEVIEVE COUNTY


Iron, IIIF, octahedrite
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Found during Fall of 1888
37° 58' N., 90° 19' W.

A single spheroidal mass of 244 kg was found by Mr. Z. Murphy, a surveyor, ~1 mile west of the hamlet of Punjaub, which is near present-day Lawrenceton, Missouri. The St. Genevieve mass was bought by Ward several years later. Because of the long terrestrial age, several mm has been removed from the surface and terrestrial oxides are evident.

Group characteristics of the IIIF magmatic irons include very low-Co, high-Cr, and low-P contents. Other meteorites constituting group IIIF include Moonby, Clark County, Nelson County, and Oakley. In their paper ‘Chemical classication of iron meteorites–VIII’, Wasson and Scott (1975) determined that Oakley was the fifth member of a common grouping, which was thereby established as group IIIF. Since then the number of irons in this group has increased to nine.

Notably, the pyroxene pallasite Zinder was found to contain metal with a composition that closely matches that of group IIIF irons, and further analyses of IIIF iron samples could help resolve any potential genetic relationship that exists (Boesenberg et al., 2017). The specimen of St. Genevieve shown above is a 55.4 g etched partial slice exhibiting a fine to medium Thomson (Widmanstätten) structure. The photo below shows the entire mass as photographed by Ward.

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