Mifflin        42°54’27"N, 90°21’56"W

Iowa County, Wisconsin, United States

Fell: April 14, 2010, 10:07 pm CDT (UT-5)

Classification: Ordinary chondrite (L5)

History: A bright fireball was seen by numerous observers in parts of Wisconsin, Iowa, and Illinois the night of April 14, 2010. A camera on the roof of the Atmospheric and Oceanic Sciences Building at the University of Wisconsin-Madison captured two images of the fireball at around 10:07 PM. The track was recorded by Doppler radar. Residents in Mifflin Township, Wisconsin, heard large explosions at the same time. The first stone recovered (7.4 g) hit the metal roof of a shed and was found the following day; it was identified as a meteorite at the University of Wisconsin-Madison. Numerous stones fell as a shower mainly in the area of Mifflin Township within a total distance of 20 km. More than 70 stones and fragments were recovered in the area within a few weeks after the fall.

Physical characteristics: Total mass recovered is more than 3.5 kg. The largest stone, 332 g, is owned by the finder and private collectors. Most pieces are fully enclosed in fusion crust.

Petrography, description, and classification (N. Kita, J. W. Valley, D. Nakashima, T. Ushikubo, M. J. Spicuzza, UWisc; G. MacPherson, L. Welzenbach, SI; A. M. Davis, UChi; P. R. Heck, FMNH). Most stones are partly to fully fusion crusted. Some broken surfaces show brecciated texture, with dark and light clasts. Black-colored shock veins up to a few mm long were observed. Chondrules are not obvious in hand specimen, but are visible in thin section.

Geochemistry: Mineral compositions and geochemistry: Olivine (Fo_75.1±0.2; n=15), low-Ca pyroxene (En_78.9±0.2Wo_1.5; n=16). Oxygen isotope analysis (Mike Spicuzza by laser fluorination/gas-source MS): δ¹⁸O=4.84‰, δ¹⁷O=3.65‰, Δ¹⁷O=1.13‰.

Classification: Ordinary chondrite (L5), shock stage S1.

Specimens: Type specimen 21.09 g, SI. Other stones at: UWisc: 142 g; FMNH: 48 g, 17.8 g, 13.1 g, 6.94 g.