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.0