Meteoritical Bulletin: Entry for Derrick Peak A78008

Writeup from AMN 2(1):
This text was reprinted from AMN 2(1) in AMN 4(1). In some cases, it may be an updated version from the original.

Sample No.: DRPA78008

Location: Derrick Peak

Field No.: 336

Weight (gms): 59400.0

Meteorite Type: Iron

Physical Description:

This sample was very clean and fresh when recovered in Antarctica, but on its arrival in Houston, the sample contained large quantities of rust. The B surface was touching the ground when the iron was discovered. Half of the B surface is covered with a thin coat of soil as is part of the T surface, an area ~8 cm in diameter. The overall color of the meteorite was metallic brownish-black while in the field, but now it is mostly reddish-brown due to oxidation. The meteorite is irregular but blocky. The surface is rough and has many regmaglypts. The deepest regmaglypts are ~2 cm deep and are on the B surface. The remaining surfaces have regmaglypts, however, they are not as deep as the ones on the B surface but they are wider. Silvery platy inclusions (schreibersite (?), cohenite (?), daubreelite (?) are randomly scattered over the entire meteorite. The meteorite is approximately 37 x 25 x 21 cm.

[Addendum to AMN 4(1)]

DRPA78008

Tentative classification: R. S. Clarke, Jr.

This is the first of the Derrick Peak irons to be examined. The highly unusual and strikingly similar external appearances of the nine specimens seen here, DRPA78001 to A78009, suggests that they are all of the same type.

An area of approximately 360 cm² of macroetched surface was examined. The dominant structural units distributed over perhaps 60% of the surface are 11 broad and irregular areas of swathing kamacite enclosing large hieroglyphic schreibersites, three of these schreibersites bordering centimeter-size troilites. Between these swathing kamacite areas are areas of coarsest octahedrite structure. Grain boundary schreibersite is common throughout the surface and lamellar schreibersites are present in many areas of kamacite. Neumann bands are abundant in the kamacite, and deformation zones are a common feature. Taenite and plessite are present in areas of coarsest octahedrite structure. Weathering has penetrated the section, particularly along grain boundaries bordering swathing kamacite areas. What appear to be cleavage cracks are present in some areas of kamacite. The specimen is a coarsest octahedrite, a Group IIB meteorite similar to Santa Luzia.