Coolidge

Kansas, United States

Find: 1937

Classification: CL4

Revised classification and description.

Petrography: Carbonaceous chondrite with high chondrule abundance (79 vol%) and low amount of fine-grained matrix (18 vol%). Composed of irregularly formed Type-I chondrules, few Type-II chondrules, refractory inclusions (CAIs, AOAs), inter-chondrule metal and sulfide grains and matrix. Contains high amounts of (partly terrestrially oxidized) metal (magnetic susceptibility log χ (× 10^-9 m³/kg) = 4.94). The mean chondrule size is: 404±405 µm (55-2790 μm; n=145). Fragments of chondrules and refractory inclusions occur, but macroscopically this sample is unbrecciated. It is of shock stage C-S2 and has a weathering grade of W2.

Geochemistry: Olivine is equilibrated with a mean value of Fa_14.5±0.4. The mean composition of low-Ca pyroxene is Fs_9.4±3.9Wo_0.9±0.1. Bulk oxygen isotopic composition: δ¹⁷O = -6.835±0.216; δ¹⁸O = -3.336±0.169; Δ¹⁷O = -5.101±0.128 per mil. Bulk Ti and Cr isotopic compositions: ε⁵⁰Ti ± 2σ = 2.63±0.10; ε⁵⁴Cr ± 2σ = 0.81±0.10.

Classification: Due to its characteristically low amount of matrix, highly depleted concentrations of volatile elements, high magnetic susceptibility, low Fa values of equilibrated olivine, and unique position in the ε⁵⁰Ti-ε⁵⁴Cr diagram, this sample was reclassified as a CL4 chondrite by Metzler et al. (2021).