CM Carbonaceous Chondrites

Cimarron (37.85° N, 100.35° W)

Gray County, Kansas USA
Found ~1948
Carbonaceous chondrite (CM2)

A single stone of unknown weight was found by a rancher on a farm 3.4 miles north of Cimarron and sent to the University of Kansas in the early 1950s. A piece was later acquired by a meteorite collector and samples given to NAU in 1998 and pieces to AMNH in 1992 and 1993. Classification and mineralogy (M Zolensky, JSC; and T. Bunch, NAU): olivine ranges from Fa₁ to Fa₆₄, with a peak at Fa_1-2, average Fa_1.2, PMD 11%. Low Ca-pyroxene ranges from Fs₂Wo₅ to Fs₅Wo₄, also present are diopside, enstatite-diopside, pigeonite, and chromite. Porphyritic olivine, barred olivine and granular olivine crystals are most abundant, maximum chondrule diameter is 2 mm. Chondrules are sparse, matrix and chondrule rims comprise ~85 vol. % of the meteorite. The percentage of matrix is similar to that of Bells and Nogoya, but the composition of these is lower in S and Mg, and higher in Si; this could be due to terrestrial weathering. Specimens: type specimen 21 g AMNH; 7.1 g, NAU.