corundum, ruby, Malawi.12, inclusions.5, gems

Describes gem-quality red and orange corundum from Malawi, material that became available in 1988 from deposits that had produced corundum since the late 1950s. The stones range from pale to dark red, with some material of fine facetable quality. Gemological examination shows variations in refractive index, birefringence and specific gravity related principally to differing chromium and iron contents. Microscopic features include growth structures with hexagonal symmetry, color zoning along growth planes, and mineral inclusions. The study characterizes the Malawi material and documents the relationship between trace-element composition, color and physical properties. A more extensive English-language study of the material subsequently appeared in The Journal of Gemmology in 1990.