In Rio Grande do Norte State, rare-element mineralized granitic pegmatites have been known since the pioneering work of Johnston (1945) and Rolff (1946) in the Borborema Pegmatitic Province. In 2006, a team led by one of the present authors discovered emeralds in the Fazenda Bonfim region (figure 1; Cavalcanti Neto and Barbosa, 2007). The team was hired by Emprogeo Ltd. (Natal, Brazil) to explore for chromium, nickel, and platinum mineralization associated with ultramafic rocks, which were known to be present but had never been properly mapped. Emeralds were found in an area where geologists had previously focused on gold and rare-element mineralization. Several mines in this region (near the municipality of Lajes) had produced beryl and/or columbite-tantalite from pegmatites, but without any attention to the potential of ores related to ultramafic rocks. After the discovery of emeralds in the Fazenda Bonfim region, Mineração Vale Verde Ltd. (registered in June 2006) acquired the mining rights from Emprogeo Ltd. Exploration of the area, which comprises nearly 656 hectares, started in August 2006. Mineração e Comércio Itaobi Ltda. also owns several licenses close to this area, and Mineração Santo Expedito Ltda. is the holder of a nearby gold, tungsten, and bismuth mining concession. All have invested heavily in mineral exploration (sampling, drilling, mapping, and geochemical surveys). Despite these efforts and promising early results, the emerald mine has not yet begun production.

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Zimbabwe's Sandawana mines have beenan important producer of emeralds for 40 years. Since the mines came under new ownership in 1993, consistent production has been established and, in addition to the small sizes for which Sandawana is known, greater numbers of polished stones as large as 1.50 ct have been produced. Currently, mining at the most active area, the Zeus mine, is done underground, with the ore processed in a standard washing/ screening trommel plant. Sandawana emeralds can be readily separated from emeralds from other localities. They have high refractive indices and specific gravities. Two amphiboles, actinolite and cummingtonite, are abundant inclusions; albite and apatite are common. Also found are remnants of fluid inclusions. Chemically, Sandawana emeralds typically have a very high chromium content.