Overview of Khatyrka Grain 126A. (a) Backscattered electron (BSE) image of Grain 126A. Bright regions are mostly Al-Cu-Fe metal assemblages; they have an irregular, cuspate-lobate appearance and consist predominantly of khatyrkite (“kh”), stolperite, and eutectoid regions (“eut”; further detail in Fig. 3) that contain a vermicular mixture of metallic Al (up to 13.3 weight% Cu) and khatyrkite. The darker regions mostly comprise crystals of olivine (“ol”; further detail in Fig. 2c and d) and spinel-group minerals with varying composition, which we call “spinel” (“sp”; further detail in Fig. 6)—all surrounded by silicate glass. (b) Al-Cu-Fe combined X-ray area map, overlaid on a BSE image. Light purple regions are Al-Cu metal (khatyrkite, stolperite); blue/dark purple regions are predominantly glass and spinel; green regions are mainly the silicate glass and crystals that grew within the melt (olivine, spinel); the relatively large white grains are predominantly Fe-Ni (appearing white because of the underlying BSE image, despite containing Fe). The different compositions of spinel manifest here as different degrees of brightness (a) and different colors (b).