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Estherville (Emmet County, Iowa, USA) Mesosiderite (stony-iron) Found 10th May 1879

A bright fireworks show announced the arrival of this witnessed fall, and the explosive detonations that followed were reported to be loud enough to stop an argument during an Estherville baseball game!

This stony-iron is called a mesosiderite - broken mantle rock of polymict breccia, composed of angular rock fragments of different compositions. Large nuggets of nickel-iron can be found in Estherville which show Widmanstatten figures (even before etching), and a wide assortment of eucritic and diogenetic stony inclusions that can reach sizes of several inches across. As their mineral compositions are unrelated, mesosiderites can be bothersome to scientists. A current theory describes the reassembly, accretion and mixing of the components after an impact event, to give the brecciated nature of this meteorite, followed by heating under pressure, melting and crystallisation over a very slow cooling period.

The larger slices listed show all of the representative features expected of Estherville. Large metal nuggets reveal Widmanstatten figures when reflected in the light (they are not etched), and HUGE clasts of eucrite and diogenite material. Some of the smaller clasts are colourless and as clear as plain glass.


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