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Thin Sections

41 grams. 58 x 56 x (3-4) mm.   Mesosiderite-A1

TKW 48.5 kg. Fall not observed. Found 1887, Tennessee, United States.

 

jnmczurich writes:

Crab Orchard is a typical mesosiderite of the trydimite-rich sub-group MES-A, similar looking like e.g. Vaca Muerta.

A nice view back into older times gives the old thin section. The Crab Orchard stony-iron meteorite was called a grahamite, a former sub-group of the mesosiderites. Powder Mill Creek (written name on the old thin section) is a synonym for Crab Orchard.

There is a nice short description of the term "grahamite" in the Mineralogical Magazine, Vol. 39, pp 204-15 (1973), Brian Mason & E. Jarosewich:

The Barea, Dyarrl Island, and Emery meteorites, and a review of the mesosiderites

The mesosiderites form a small but interesting class of meteorites. The name was introduced by Rose (1863), who defined these meteorites as 'ein körniges Gemenge von Meteoreisen und Magnetkies mit Olivin und Augit', and used the name mesosiderite to indicate that they consisted of approximately equal amounts of metal and silicate phases and thus fell midway between the major groups of iron and stony meteorites. He described two representatives of this class, Hainholz and Vaca Muerta. Tschermak (1885) proposed an additional class, which he named grahamites, defining them as consisting of plagioclase, bronzite, augite, and nickel-iron, i.e. mesosiderites with plagioclase. However, Prior (1918) showed that there was no real distinction between the grahamites and the mesosiderites, since all contained plagioclase, and recommended that the term grahamite be dropped.

University trade: 2003