The Thereza Christina Maria Collection consists of 21,742 photographs assembled by Emperor Pedro II and left by him to the National Library of Brazil. The collection covers a vast range of subjects. It documents the achievements of Brazil and the Brazilian people in the 19th century, as well as includes many photographs from Europe, Africa, and North America. In 1868, the photographer Augusto Riedel took part in an expedition to the interior of Brazil that visited several mining towns. This photograph, taken by Riedel, shows a mine on the Jequitinhonha River, which begins in Serro, Minas Gerais, and flows to the Atlantic. Diamond mines and mining; Memory of the World; Slave labor