Porangatu deposit, Porangatu, Goiás, Brazil
The Porangatu deposit is controlled by the same regional fault that controls Santa Terezinha deposit. Beryl, including emerald, is in metasomatic zones of metamorphosed ultramafic rocks in pegmatite, quartz, and quartz-oligoclase veins.The dark green emeralds are hosted in glimmerites as small crystals 0.5 to 1 cm long. Pegmatites are characterized by colourless beryls, and the quartz-oligoclase and quartz veins contain pale green and bluish beryls.
Ref: E.Ya. Kievlenko (2003) Geology of gems, p. 92