Morphology of Colombian Emerald: Some Less-Common Cases and Their Growth and Dissolution History

Abstract

GEMS & GEMOLOGY SPRING 2023 In general, the morphology of Colombian emerald originating from different mines is rather simple and formed by a small number of external crystal faces. We observe two dominant planes, the basal pinacoid and the first-order hexagonal prism, occasionally in combination with small second-order hexagonal prism faces and firstand/or second-order hexagonal dipyramids (Goldschmidt, 1913; Schwarz and Giuliani, 2002; Moore and Wilson, 2016). The internal growth pattern of such samples, which normally show prismatic habit, consists of growth planes parallel to the external crystal faces (Kiefert and Schmetzer, 1991). Occasionally, natural emerald and beryl crystals show etching and dissolution features (an overview of the pertinent literature is given in box A). Other growth features are due to skeletal and polygonal growth of beryl crystals (see box B). Both growth features are related to the observations made in this article for Colombian emerald crystals. Rarely mentioned are emerald crystals with conical habit (Johnson, 1961a,b)—or vasos in the form of slightly conical empty tubes (Klein, 1941)—or emeralds in the form of prismatic, empty “cups” with planar bottoms (Weldon et al., 2016). In most references,