Pallasite, PMG-am (main-group, anomalous metal composition)
40° 16' N., 94° 41' W.
Employing a technique often utilized by famed meteorite hunter Harvey Nininger, Karl Aston distributed flyers around his Missouri farming community. In 2006, a 17 kg mass (held by Dr. Randy Korotev) was discovered embedded 90% in the ground near Conception Junction, MO. The mass was brought to the attention of Aston who identified it as a pallasite meteorite. The meteorite was subsequently acquired from the landowner with the assistance of Dave Gheesling. Although a thorough search was conducted with the help of meteorite hunter Robert Ward, no further masses were found.
Initially, a section of the pallasite was examined by Randy Korotev (Washington University), while an in-depth analysis was conducted by John Wasson (UCLA). The Conception Junction pallasite was determined to be a unique main-group member having anomalous metal chemistry. On elementAu diagrams, Conception Junction plots well below most main-group members for Ni and Cu, and above most main-group members for Co, Ga, As, and Ir. Click here to see a diagram comparing olivine chemistry among main-group members and the unique Milton pallasite. The mostly rounded olivine crystals have diameters that average 4.5 mm, which is among the smallest of all pallasites; this small size reduces translucency in thin slices.
A historical monograph titled "CONCEPTION JUNCTION PALLASITE, MO." has been written by Gheesling and Wasson. The specimen shown above is a 3.95 g slice cut by Marlin Cilz at the Montana Meteorite Laboratory on a wire saw. The photo below was taken after the first sectioning through the weathered exterior of the mass.