Sample No.:	RBT 04261; RBT 04262
Location:	Roberts Massif
Field No.:	16331; 15145
Dimensions (cm):	4.0x3.5x2.5; 6.5x5.5x3.5
Weight (g):	78.763; 204.6
Meteorite Type:	Shergottite

Macroscopic Description: Kathleen McBride
30-50% of the exterior surfaces have brown/black, rough textured fusion crust with glassy spots. The interior is soft and tan-gray in color with a sandy texture and low metal content.

Thin Section (,2) Description: Tim McCoy and Valerie Reynolds
These meteorites are so similar that a single description suffices. The sections are composed of a coarse-grained assemblage of pyroxene, olivine and maskelynite with grain sizes reaching up to 4 mm. Sulfides and oxides are present, as are shock melt veins and pockets. Olivine is Fa_28-40; pyroxenes exhibit a range of compositions from pigeonite to augite (Fs_16-32Wo_7-38; Fe/Mn ~ 22-30); feldspar is intermediate in composition (An_30-55). The meteorites are olivine-phyric shergottites.

Oxygen Isotope Analysis: D. Rumble
Analysis for two subsamples of RBT 04261 give: A) δ¹⁸O = +4.28, δ¹⁷O = +2.56, and Δ¹⁷O = 0.314; B) δ¹⁸O = +4.45, δ¹⁷O = +2.66, and Δ¹⁷O = 0.322. These values plot just above the terrestrial fractionation line, and are similar to many previous analyses of shergottites.

Thin Section Images

Cross-Polarized Light RBT 04261	Plane-Polarized Light RBT 04261

Cross-Polarized Light RBT 04262	Plane-Polarized Light RBT 04262

Lab Images