Pedro II (Pedro Segundo), named after Brazil's last Emperor. The city has the only mined opal deposit in South America. A mine in Peru closed a few years ago. Opals were discovered here in 1930 by a man who was washing a cassava for his lunch. The strange stone was sent to Teresina where it was identified as an opal.
^"Divisão Territorial do Brasil" (in Portuguese). Divisão Territorial do Brasil e Limites Territoriais, Instituto Brasileiro de Geografia e Estatística (IBGE). July 1, 2008. Retrieved December 17, 2009.