English: Images of sample 1174C. (a) BSE image and transmitted-light photomicrograph showing colour, and distribution of highest-Cr parts (light areas in BSE). Note ball of chromium (Cr0) on edge of crystal. (b) 3D oblique view and compositional map of the surface of 1174C before sectioning. Rough dark green in lower part of the image is the ruby; smooth dark green in the upper part is kahlenbergite (KAl11O17). Small bright grains along rim of crystal in middle of image are Ni-bearing iron. Bright pink-purple “mushrooms” are chromium. (c) Phase map and Al map of the contact between the largest Cr ball, showing higher Cr (lower Al) toward the Cr ball, and the compositional granularity of the high-Cr zone. (d) TEM-BSE image and element maps of FIB foil across contact between chromium and Cr-rich corundum, separated by a zone of oreillyite (scale bar indicates 2 μm). Note granularity in the Cr and Al maps of the corundum, interpreted as the result of spinodal breakdown. The image is published in an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).