METEORITES

 

Description: Meteorites are a diverse group of rocks. Iron meteorites and are dominated by iron-nickel alloys. Others, called stony meteorites, contain mostly mafic silicates such as pyroxene and olivine with or without carbonaceous materials. Meteorites are called "falls", where the meteorite is actually observed to fall to the ground. Those recovered later are called "finds." Most finds are the irons, which are easily identified and somewhat resistant to weathering. Falls are about evenly divided between stony and iron meteorites. As should be expected, meteorites have been found throughout the state. Any anomalies in distribution relate more to human population density than anything else.

 

Increae Lapham

 

Distinguished Wisconsin naturalist Increase Lapham examines a Wisconsin meteorite

 

CLARK COUNTY: Two stony meteorites with a combined weight of over 200 lbs. fell at 6:15 P.M. on July 4, 1917 near Colby (Read, 1962). Samples of the Colby meteorite are in the Geology Museum at U. W. - Madison.

COLUMBIA COUNTY: A 772 gram stony meteorite fell through a barn roof near Kilbourn at 5:00 P.M. June 16, 1911 (Read, 1962). Specimens and a replica of this meteorite are in the Geology Museum at U. W. -Madison.

KEWAUNEE COUNTY: A meteorite massing nearly 4 kg. was found during plowing on a farm about 4 miles west of Algoma. It contained 88.6% Fe and10.6% Ni. It was described as an "octahedral siderite rich in kamacite and taenite and relatively poor in plessite." with internal schreibersite bands, Widmannstatten figures, Neumann lines and Reichenbach's lamellae (Hobbs, 1903). This meteorite is now in the Geology Museum at U. W. -Madison.

LAFAYETTE COUNTY: A stony meteorite weighing 58.28 lbs. was found in 1958 near Belmont. It contained mostly bronzite and olivine, but also contained about 23% Fe-Ni alloys (Broughton and LaPaz, 1962). The Belmont meteorite is currently in the Geology Museum at U. W. -Madison.

SHAWANO COUNTY: A 33 lbs. iron meteorite was found in 1916 during plowing on a farm approximately 3 miles north of Angelica (Read, 1962a).

ST. CROIX COUNTY: An iron meteorite massing 24,000 grams was recovered from a plowed field (N1/2 SW Sec. 31 T.29N R.17W) near Hammond in 1884. Troilite was present in nodules and as fracture fillings. Chemical analysis gave 89.78% iron and 7.6% nickel with trace amounts of cobalt, phosphorous, silicon, carbon, copper and tin (Fisher, 1887).

VERNON COUNTY: The "Claywater Meteorite" was observed to fall at 9 A.M. on March 25, 1865. It came in as a rotating fireball and exploded near ground level. Two fragments with a combined mass of 1500 grams were recovered. The meteorite was mostly stony, containing olivine and enstatite. It also contained about 17% Fe-Ni alloys (Smith, 1876).

WALWORTH COUNTY: The "Zenda Meteorite" was found in 1955, about a half mile west of Zenda. It massed 3.7 kg. and was deeply oxidized. It was an iron meteorite containing kamacite, schreibersite patches, troilite, taenite and lawrencite. It also contained minor graphite, olivine and pyroxene (Read, 1963).

WASHINGTON COUNTY: A number of large fragments of an iron meteorite have been found in Trenton township, east of West Bend. Fragments were originally found in 1858. More fragments turned up in 1873. A detailed search of the area with a metal detector turned up more fragments in 1952 and 1964. At least 13 fragments had been found so far. The largest chucks weighed 527 lbs. and 413 lbs. The most recent finds were made in the NE Sec. 33 T.11N R.20E. Sawn and treated fragments show troilite nodules and lenses (Irving, 1882; Lapham, 1877; Smith, 1869; Read and Stockwell, 1966). Specimens from this meteorite are in the Geology Museum at U. W. -Madison.

WAUSHARA COUNTY: An iron meteorite with stony inclusions was found in 1894 near Saxeville, Sec. 8 T.20N R.2E. Its mass is 3600 grams (Perry, 1944; Read, 1962). This proved to be an unusual meteorite that was named the "Pine River Meteorite." It is an octahedrite with many silicate inclusions and an "anomalous member of chemical group IA." The silicate inclusions consist of "granular crystalline intergrowths of orthpyroxene, olivine, plagioclase feldspar, troilite and iron nickel metal with accessory chromite, diopside and schreibersite" (Beavar and Grady, 1988).

- A stony meteorite massing 676 grams was found near Mt. Morris at 44o N 89o15'W (Buckstaff, 1962). The Mt. Morris Stone is a coarsely crystalline sulfide rich stone with forsterite, enstatite, kamacite, schreibersite, troilite, graphite, chromite, daubreelite and chalcopyrite (Bild, 1977). Later detailed geochemical suggests that the Mt. Morris meteorite is a fragment from the Pine River Meteorite (Beavan and Grady, 1988).

WINNEBAGO COUNTY: A 1/4 lb. fragment of stony meteorite was found on gravel approximately 2 miles NW of Oshkosh (Read, 1962).

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