Yucca 047        34°49.281’N, 114°16.655’W

Arizona, United States

Find: 24 Nov 2011

Classification: Ordinary chondrite (H3-6)

History: Found with metal detector in the Yucca DCA by Jim Wooddell November 24, 2011. Entire stone donated to Cascadia.

Physical characteristics: Exterior is covered with a brownish weathering patina.

Petrography: In thin section, the sample appears to be a relatively integrated mixture of chondrules, chondrule fragments, and indistinct fragments of chondritic clasts. The section appears dark due to the size of small fragments and individual grains that make up material interstitial to chondrules and larger fragments. One discrete lighter colored clast is visible, which lacks discernable chondrules, and contains coarse grains of feldspar (most slightly below 50 µm in diameter, but a few larger grains). BSE imaging shows that the meteorite contains a mix of equilibrated silicates, with a fairly large (~25-35 area %) admixture of type 3 material (both magnesian and iron-rich olivine and pyroxene grains). Free copper, an FeNi carbide, and magnetite are present, as well three grains of low-Ca pyroxene with relatively high (3.6-5.8 wt% Al₂O₃) alumina content, similar to those reported for Buck Mountain Wash. Small chromite-plagioclase objects are present. Opaques show minor weathering (~5-10% replacement by Fe-hydroxides). Shock effects in olivine are variable from sharp optical extinction to a recrystallized clast, but most olivine grains in the section show undulose extinction with one set of planar fractures, indicating a shock stage of S3.

Geochemistry: (M. Hutson and A. Ruzicka, Cascadia) Host lithology olivine (Fa_19.2±7.0, N=50) and low-Ca pyroxene (Fs_13.1±5.4Wo_0.9±0.8, N= 47) compositions reflect the large admixture of type 3 material. A clast of higher type material has equilibrated olivine (Fa_19.1±1.2, N=8) and low-Ca pyroxene (Fs_17.0±0.7Wo_1.8±1.0, N=10) compositions.

Classification: H3-6 finely intermixed genomict breccia. Type 5-6 lithology implied by medium to coarse feldspar grain sizes and equilibrated olivine and pyroxene; type 3 lithology implied by common presence of magnesian and zoned olivine. Paired with Buck Mountain Wash (synonymous with Yucca 002) on the basis of mineralogy, mineral chemistry, and texture.

Specimens: Cascadia holds 11.3 g in a single piece, in addition to one polished thin section and a mounted butt.