Creston, Fresh L6 Hammer Fall from California 2015, Micromount

$5.00
Creston, Fresh L6 Hammer Fall from California 2015, Micromount

Description

On the night of October 23, 2015, a large, multi-colored fireball lit up the night sky over parts of California. Witnesses across the Paso Robles area and San Luis Obispo county reported seeing the fireball break up, and some people heard sonic booms. Several sky cameras captured the trajectory of the bolide and meteorite hunters began to identify the expected strewnfield area. The first stones were found before the rains and one of those stones had struck a metal fence post and shattered into many pieces. Later analysis showed the meteorite to be a shocked L6 chondrite. There was only a modest of amount of meteorites recovered, due in part of the difficulty of searching the terrain, so very little is available to collectors. Out of less than 700 grams total, most is held by the finders or scientific institutions, with only a few small slices and micromounts on the open collector market. The specimens I am offering here come from Robert Ward's hammer stone that struck the fence post.

Refer to the photo. The black centimeter cube is shown for scale and is not included. You are purchasing a small fragment like the one shown. Your purchase will include a labeled gemjar for safe storage.

From the Meteoritical Bulletin entry on Creston :

Creston 35°34’13"N, 120°28’21"W

California, United States
Confirmed fall: 2015 Oct 23
Classification: Ordinary chondrite (L6)

History: (Robert Ward, Anne Marie Ward, Robert Matson, Marc Fries) On 23 October at 22:47 PDT (24 October 2015, at 05:47 UTC) a large fireball lit up the rolling hills of wine country east of Paso Robles. The bolide displayed a multitude of colors as it broke up. The fireball was captured on at least four all-sky cameras in Parker, Arizona; Riverside, California; El Segundo, California; and the SETI Institute CAMS all-sky system in Sunnyvale, California. Dozens of witnesses close to the ground path heard sonic booms shortly after the fireball terminated. Confirming these accounts, sonic boom signatures were recorded by three California seismic stations, allowing triangulation of the approximate fall zone. Six Doppler radar returns acquired from the NOAA NEXRAD weather radar network were used to further constrain the fall location. The earliest radar signature appears in imagery from the KVTX (Los Angeles, California) radar at an altitude of 16.2 km above sea level (ASL) at 05:47:57.6 UTC - just 12 s after the meteor first appears in the Riverside video. KVBX (Vandenberg AFB, California) recorded signatures of falling meteorites at 05:49:40.3, 05:51:08.9 and 05:53:43.3 UTC at altitudes of 5.6 km, 6.7 km and 1.2 km, respectively; KHNX (San Joaquin, California) recorded several returns at 05:51:57.3 at an altitude of 3.9 km. Finally, KMUX (San Francisco) recorded a pair of returns at 16.2-km altitude at 06:00:41.7. This last return is likely the signature of fine dust, given its altitude and timing, which correlates with eyewitness accounts of a visible smoke trail left by the fireball. Based on the relative timing and altitude of the earlier five radar returns, the estimated masses of falling meteorites at those locations vary from sub-gram to as much as 10 kg for the earliest return. Equipped with the radar-cued search area, Robert and Anne Marie Ward located the first stone on 27 October, along the road (California Route 41), 7.3 km northeast of Creston, San Luis Obispo County. The stone broke upon impact, with a total mass of 395.7 g. As of 10 November, 108 g, 102 g and 82 g stones have also been recovered.

Physical characteristics: Stone covered with matte to shiny black fusion crust up to 1 mm thick. Exterior rounded with a few broad regmaglypts. Chondrules not visible. Stone criss-crossed with shock veins, some to 2 mm thick. Sample also broke along well-developed slickenside surfaces that are shiny and black.

Petrography: (L. Garvie, ASU) A polished microprobe section shows dominantly coarse-grained recrystallized minerals. Only two BO chondrules were recognizable in the section. Plagioclase abundant to 200 μm. Chromite grains to 300 μm are anhedral with rounded outlines. Troilite grains to 300 μm and largely single crystal and lacking shock lamellae except where near shock veins. Scattered Ca-Cl and Ca-Mg-Na phosphates to 200 μm. Fe-Ni metal grains to 400 μm. Metal grains range from kamacite with weakly developed Neumann bands, to polycrystalline, to those with tetrataenite rims and cores of dark-etching plessite or acicular kamacite. Section shows a well-developed 1-mm thick shock vein with 50-μm blebs and spheres of Fe/Fe-S. Fine-grained melt pockets are present but rare.