Erythrite, an attractive secondary mineral often seen as pink crusts and films formed during the oxidation of cobalt arsenide-bearing veins, was described in a recent Connoisseur's Choice (Cook 2007). Although annabergite (the analogous nickel mineral) is far less common in fine specimens, it too is well known to collectors, particularly micromounters. Interestingly, on rare occasions both species can be found in the same deposit and even on the same specimen, with the contrasting greens of annabergite and the reds of erythrite resulting in attractive and unusual specimens. Because of its wide distribution and particular interest to micromount and thumbnail collectors, annabergite has been chosen for this issue's Connoisseur's Choice species.
Dr. Robert B. Cook, an executive editor of Rocks & Minerals, is a professor emeritus in the Department of Geology and Geography at Auburn University, Auburn, Alabama.