The Museu do Diamante occupies a colonial building in the historic centre and covers the full arc of Diamantina's diamond history — from the initial discoveries in the 1720s through the Portuguese monopoly system, the slave labour that did the actual mining, and the eventual decline when South African mines undercut Brazilian production in the late 19th century.
The collection includes mining tools, maps of the diamond districts, documents from the royal monopoly administration, and a section on the social history of slavery in the region. It is not a flashy museum, but for understanding the economic and human reality behind the handsome colonial architecture, it is essential.