Yucca 035        34°42.063’N, 114°11.259’W

Arizona, United States

Find: 2005 Oct 9

Classification: Ordinary chondrite (H3-6)

History: Dennis Asher found this stone on October 9, 2005, and later donated it to Cascadia.

Physical characteristics: All surfaces are covered with weathering products, consisting of patches of orange rust, tan clay and pink caliche. No remnant fusion crust is present.

Petrography: In thin section, composed mostly of an intimate mixture of mineral and chondrule fragments with diverse (type 3-6) characteristics; one discrete type 6 clast is also present. BSE imaging shows that most of the rock ("host") is composed of type 4-6 lithologies, with equilibrated olivine, and plagioclase varying from smaller (to 50 µm across) to rarely coarser (>100 μm) grains; the host also contains ~5-10% material characteristic of type 3 including zoned or more magnesian and ferroan olivine grains, feldspathic glass, and magnesian pyroxene. Discrete type 6 clast contains coarse feldspar (50-100 μm grains). Individual grains of a silica polymorph were observed, as well as three grains of low-Ca pyroxene with relatively high (3.4-4.7 wt% Al₂O₃) alumina content, similar to those reported for Buck Mountain Wash. A number of small chromite-plagioclase objects are present, as are grains of metallic copper. Many fragments and metal and troilite roughly align. Opaques show minor weathering (~5-10% replacement by Fe-hydroxides). Shock effects in olivine are variable across the section, with most grains having undulose extinction and one set of planar fractures, consistent with a shock stage of S3.

Geochemistry: (M. Hutson and A. Ruzicka, Cascadia) Host dominated by equilibrated olivine (median Fa_18.9, N=127), and low-Ca pyroxene (median Fs_15.3, N=86), but also containing more magnesian and ferroan olivine (Fa_2.1-51.2) and low-Ca pyroxene (Fs_5.7-30.8). Overall average host including mixture of both equilibrated and more varied compositions is olivine (Fa_19.6±5.8, N=127), low-Ca pyroxene (Fs_13.4±5.7Wo_1.3±1.3En_85.3±5.8, N= 86). Type 6 clast olivine (Fa_19.4±1.3, N=7) and low-Ca pyroxene (Fs_17.1±0.5En_81.2±1.0Wo_1.7±0.6, N=4).

Classification: H3-6 finely intermixed genomict breccia. Type 5-6 lithology implied by larger feldspar grain sizes and abundant equilibrated olivine and pyroxene as well as discrete type 6 chondrite clast; type 3 lithology implied by common presence of magnesian and zoned olivine and feldspathic glass. Paired with Buck Mountain Wash on the basis of mineralogy, mineral chemistry, and texture.

Specimens: Cascadia holds 35.9 g in multiple pieces, in addition to two polished thin sections and a mounted butt.