Diamantina is a Brazilian municipality in the state of Minas Gerais. Its estimated population in 2020 was 47,825 in a total area of 3,870 km²…Diamantina is a Brazilian municipality in the state of Minas Gerais. Its estimated population in 2020 was 47,825 in a total area of 3,870 km². Arraial do Tijuco was built during the colonial era in the early 18th century. As its name suggests, Diamantina was a center of diamond mining in the 18th and 19th centuries. A well-preserved example of Brazilian Baroque architecture, Diamantina is a UNESCO World Heritage Site.