Socotó mining district, Campo Formoso, Bahia, Brazil
40 km NE of the Carnaiba deposit.Emeralds are in a block of metamorphosed ultramafic and volcanic rocks 3.5 km long and about 500 m wide, enclosed in adamellite granites of the late Proterozoic Campo Formoso massif. Dolomitized serpentinites, talc rocks, and amphibolites of this large xenolith host pegmatite veins and metasomatic zones of biotite-phlogopite rocks with light-green beryl and emerald associated with scheelite, molybdenite, phenakite, chromite and tourmaline. The physical properties, chemical composition and inclusions of the Socoto emeralds are similar to those of the Carnaiba deposit. Their typomorphic features are inclusions of carbonates (calcite, dolomite, breunnerite), thin tube-shaped channels, and finely-banded, zoned colour (Eidt and Schwarz, 1990).
Ref: E.Ya. Kievlenko (2003) Geology of gems, p. 91