Yucca 033        34°44.213 N, 114°13.722 W

Arizona, United States

Find: 2004 Apr

Classification: Ordinary chondrite (H3-6)

History: Jerry A. Baird purchased the meteorite from a finder, and later donated the entire stone to Cascadia.

Physical characteristics: Brownish weathering patina occurs on broken exterior surfaces. Weathered fusion crust covers one side. Three large (0.3 to 0.7 mm across) metal grains containing angular silicates are visible on a cut face, along with numerous much smaller metal grains.

Petrography: In thin section, the sample appears to be relatively integrated, with many chondrule fragments and only a few complete chondrules present; distinct clasts typical of a breccia are absent. The material between chondrule fragments is composed of individual grains and smaller fragments. BSE imaging shows that most of meteorite contains equilibrated silicates, but that there is a fairly large (~10-15 area %) admixture of type 3 material (both magnesian and iron-rich olivine and pyroxene grains). Most of the equilibrated material contains devitrified glass or medium-sized (up to 50 µm) plagioclase feldspar grains, although a few fragments contain coarse (>100 µm) plagioclase grains. Laths of a silica polymorph were observed, as well as two grains of low-Ca pyroxene with relatively high (4.1 – 4.4 wt% Al₂O₃) alumina content, similar to those reported for Buck Mountain Wash. Small chromite-plagioclase objects are present. Many fragments and metal and troilite grains show a rough alignment across the section. 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. Shock melt with zoned olivine grains set in glass is present.

Geochemistry: (M. Hutson and A. Ruzicka, Cascadia) Dominated by equilibrated olivine (median Fa_18.9, N=164) and low-Ca pyroxene (median Fs_15.3, N=98). Overall average including mixture of both equilibrated and more varied compositions in different lithologies is olivine (Fa_{18.2 ± 4.9}, range Fa_0.9-35.9, N=164), low-Ca pyroxene (Fs_13.0±6.2Wo_1.0±0.9En_{86.0± 6.2}, range Fs_0-24.7, N= 98).

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 on the basis of mineralogy, mineral chemistry, and texture.

Specimens: Cascadia holds 102.5 g in multiple pieces, in addition to two polished thin sections and a mounted butt.