Cat Mountain

L Impact-Melt Breccia
(L5 in MetBull 75)
standby for cat mountain photo
Found 1980/81, recognized 1993
32° 8.9′ N., 111° 6.7′ W. In Tucson, Arizona, a man named William Goldups walked his dog along the same path near his home on a daily basis. One day he discovered a rather large, dark stone that had not previously been there. He brought it home and placed it on his mantle where it remained until after his death in 1990. The rock was inherited by a friend, who took it to the University of Arizona’s Mineral Museum. An X-ray powder diffraction test determined that olivine was present. The meteorite was then taken to the Lunar and Planetary Laboratory (D. Kring) where it was analyzed by electrom microprobe and reflectance spectrography, which conclusively determined that it was a meteorite. The name Cat Mountain corresponds to the southern-most peak of the Tucson Mountains, located about 2 miles NW from the site of the find. In 2011 two additional paired stones were recovered on Snyder Hill, a few hundred yards from the location of the main mass. These include a 107.2 g stone found in March by Mike Holden and classified as Cat Mountain 001 (Bunch and Wittke, NAU), and a 162 g stone found in August by Count Guido Deiro and classified as Cat Mountain 002 (Bunch and Wittke, NAU).

This is an unusual meteorite that has undergone numerous impact/heating events. This impact melt breccia contains chondrule-bearing clasts preserving shock veins from an early impact on its parent body, perhaps 2.7 b.y. ago. Thereafter, another impact metamorphosed the chondrule-bearing clasts to type L5. Then, 880 m.y. ago, a major impact created a melt-breccia lens at the bottom of a crater at least 1 km in diameter. The clasts were then surrounded by the swirls of an FeNi-metal melt-matrix and underwent cooling. A further impact 500 m.y. ago ejected this impact melt breccia from the surface, where it drifted in space until 20 m.y. ago. At this time, the CRE age began to accumulate, as a final collision reduced the object to a meter-sized object prior to its impact on Earth. At least six impact events are recorded in the complex history of this meteorite.

The belief by Mr. Goldups that this was a fall within 24 hours of his discovery was confirmed by reflectance spectra tests. The specimen shown above is a 4.1 g partial slice showing the boundary region between a shocked, chondrule-rich lithology and the FeNi-metal swirls of shock-melted matrix. The photo below was taken at an angle which highlights the metal flakes. standby for cat mountain main mass photo
Photo credit: Terri Haag, ‘Chasing Cosmic Rain’, Lapidary Journal, p. 47, April 1994

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