Portales Valley NM Meteorite - Complete Individual

Portales Valley

Roosevelt County, New Mexico, USA

Fell 1998 June 13, ~07:30 MDT (~13:30 UT)

Ordinary chondrite (H6)

After detonations were heard and smoky trails seen in the sky, a shower of meteorites landed near Portales, New Mexico. 53 objects have been recovered, with a total mass of 71.4 kg. The largest pieces weighed 16.5 kg (witnessed to fall by Nelda Wallace and Fred Stafford), 17.0 kg (found by Elton Brown), and at least nine others over 1 kg. A 530 g fragment went through the roof of Gayle Newberry's barn and embedded itself in a wall, indicating a trajectory west to east. The elliptical strewn field is approximately 7.7 ´ 2 km, trending N60–65ºE, although recent reports may extend this somewhat. Mineralogy (D. A. Kring, J. D. Gleason, and D. H. Hill, UAz ): olivine, Fa_{19.3 ±0.4}; pyroxene, Fs_{17.2 ±0.3} Wo_1.36±0.27; kamacite contains 0.55 ± 0.03 wt% Co; compositions indicate H-chondrite affinity; olivine indicates shock stage S1, plagioclase indicates S2–S3, and abundant opaque shock veins suggest S3 or higher (discrepancies may be due to annealing).  Macroscopic description (D. A. Kring, UAz ): Some individuals are crosscut by an unusually high number of metal-rich shock veins, and some specimens are composed dominantly of metal. These metal-rich samples appear to be large single veins, or pockets of metal produced by intersecting veins. Angular chondritic clasts may have moved a few millimeters along metal-rich veins.  Etching of centimeter-sized metal areas reveals a fine Widmanstätten pattern, bandwidth = 0.02 to 0.81 mm (average 0.32 mm). The composition of kamacite in metal-rich regions is the same as metal in chondritic areas (0.56 ± 0.05 wt% Co). The source of the metal in the shock veins appears to be the H-chondrite host, which is depleted in its normal complement of metal (4.4% rather than 15–19%). Specimens: type specimen, 49 g, and thin section, UAz; 16.5 kg mass purchased by consortium including FMNH, SI, UCLA, and UNM. 17.0 kg mass with finder; much of remaining material is being sold by commercial meteorite dealers.