McKinney meteorite, Collin Co., Texas, USA
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|Latitude & Longitude (WGS84):||33° 10' 59'' North , 96° 43' 0'' West|
|Latitude & Longitude (decimal):||33.18333,-96.71667|
|Non-native locality type:||Meteorite|
|Meteorite Class:||L4 chondrite meteorite|
|Meteoritical Society Class:||L4|
|Metbull:||View entry in Meteoritical Bulletin Database|
|Köppen climate type:||Cfa : Humid subtropical climate|
Ordinary Chondrite, highly shocked (L4; S6)
Find, 1870; 150 kg
Two stones, the larger with a mass of ~100 kg, were found. The interior has been blackened by severe shock. Chondrules of diverse textures (up to 2 mm in diameter) are present. Troilite is found both as walnut-sized nodules and in irregular veins. Olivine (Fa24) and pyroxene composition are indicative of the L (low bulk iron) ordinary chondrite chemical group. The overall composition and primary mineralogical constituents of McKinney appear quite normal. However, for the past several decades the textural variations due to multiple impacts and subsequent terrestrial weathering has drawn continuing interest (See citations below.). Ar-Ar studies, in particular, suggest that the McKinney masses had experienced multiple impacts on its long journey from a presumed original parent body to the Texas plains. Porosity studies suggest that once arriving on earth the meteorite's pores were gradually filled with weathering products making it considerably more compact than most meteorites.
Two large masses in the 40-50 kg range were obtained by the Field Museum of Natural History in Chicago and the Naturhistorisches Museum in Wiens [Vienna]. Several institutions obtained masses in the 5 kg range (including Arizona State University and the Monnig Collection at TCU).
What's in a name?? — The proper unique name for the meteorite according to the Meteoritical Society is the 'McKinney' meteorite (as above). However, in 1954 a 1.68 kg fragment of the Sylacauga, Alabama meteorite fell near the home of a Mr. McKinney. This stone is sometimes referred to the 'McKinney fragment' with 'McKinney' serving as a synonym for Sylacauga.
7 valid minerals.
Meteorite/Rock Types Recorded
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Farrington, O.C. (1915). Catalogue of the meteorites of North America: Memoirs of the National Academy of Sciences, Vol. 13: Washington. 545 pages.
Prior, G.T. (1923) Catalogue of Meteorites: with special reference to those represented in the collection of the British Museum of Natural History. Richard Clay & Sons, Limited: Bungay, Suffolk.
Mason, B. (1963) Olivine Composition in Chondrites: Geochimica et Cosmochimica Acta 27(9): 1011-1023. (Sept 1963).
Dodd, R.T. & Calef, C. (1971) Twinning and intergrowth of olivine crystals in chondritic meteorites: Mineralogical Magazine 38: 324-327. (Sept 1971).
Ramdohr, P. (1973). The Opaque Minerals in Stony Meteorites. Elsevier Publishing Company: Amsterdam; London: New York. 245 pages.
Dodd, R.T. & Jarosewich, E. (1979) Incipient melting in and shock classification of L-Group chondrites: Earth and Planetary Science Letters 44(2):335-340. (Aug 1979).
Graham, A.L., Bevan, A.W.R. & Hutchison, B. (1985) Catalogue of Meteorites (4/e). University of Arizona Press: Tucson.
Bennett, M.E. & McSween Jr, H.Y. (1996) Shock feature in iron-nickel metal and troilite of L-group ordinary chondrites: Meteoritics & Planetary Science 31(2): 255-26. (March 1996).
Alwmark, C., Schmitz, B., Holm, S., Marone, F. & Stamponi, M. (2011) A 3-D study of mineral inclusions in chromite from ordinary chondrites using synchrotron radiation X-ray tomographic microscopy—Method and application: Meteoritics & Planetary Science 46 (8): 1071–1081. (Aug 2011).