Homestead meteorite, Iowa Co., Iowa, USAi

Regional Level Types
Homestead meteorite	Meteorite Fall Location
Iowa Co.	County
Iowa	State
USA	Country

Ordinary chondrite (L5,br; S3; W0)
Fell, 12 February 1875: ~10:30 PM; 226.8 kg, meteorite shower

Late in the evening on a clear winter night, an unusually bright bolide was seen over a 600 km long path moving from the SE towards the NE over northern Missouri and southern Iowa. Detonations were heard — and, on the third day afterwards a single stone was found lying on the snow. After the snow had melted in March and in subsequent months over 300 meteoritic stones were recovered over a 10x5 km ellipse. Almost all the stones were covered with a black fusion crust. The mass of the largest stone largest stone was 33.5 kg, but a large number of very small stones were found.

The Homestead meteorite is a thoroughly brecciated meteorite. Presumably at least partially due to earlier pre-terrestrial impacts, the meteorite had already begun to break into smaller fragments well before it struck the earth. Its largely equilibrated olivine and low Ca-orthopyroxene (Fa23.1; Fs20, resp.) and its indistinct chondrules are characteristic of type L5 chondrites. Chondrules (mostly barred olivine [BO], porphyritic olivine [PO], and porphyritic pyroxene [PP]) are similar to those in many meteorites. In addition to the dominant olivine and pyroxene of both chondrules and matrix, minor amounts of Fe-Ni metal and troilite (almost entirely as aggregates within the matrix) account for most of the mass. Lesser amounts of albitic plagioclase plus accessory chromite and phosphate are present. However, close studies of textures and accessory constituents provide clear evidence of pre-terrestrial disruption. Small veins, minute pools of opaques, and weak mosaicism in olivine are but the most obvious indicators of preterrestrial shock (level S3). Whether pre-terrestrial post-shock annealing has partially obscured even stronger shock event(s) is a somewhat open question.

The L (relatively low in total iron) chondrites are the largest group of ordinary chondrites and represent ~45% of classified and witnessed falls. The L5 petrologic type subgroup represent ~20 % of the total L group. Although a few more massive L5 finds have been found, Homestead is in fact the most massive of the 80 witnessed and documented meteorite falls classified exactly as 'L5' chondrites (as of early May 2016).

The largest stones and fragments of the Homestead shower were acquired by museums in the United States (Yale University; Field Museum of Natural History in Chicago; Harvard University; American Museum of Natural History in New York). However, moderate sized masses in the 1-5 kg range were distributed to several other U.S. and European museums and institutions.

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