A Very Early Mineralogical Survey of Brazil, Showing the First Diamond Mines of the New World

William Maclure was an American/Scottish geologist, cartographer and philanthropist.  He is known as the “father of American geology.”

Maclure had a highly successful mercantile career, making a fortune that allowed him to retire in 1797 at the early age of 34 to pursue his scientific, geological and other interests. In 1807 he commenced the self-imposed task of making a geological survey of the United States. Almost every state in the Union was traversed and mapped by him, the Allegheny Mountains being crossed and recrossed some 50 times. The results of his unaided labours were submitted to the American Philosophical Society in a memoir entitled "Observations on the Geology of the United States" explanatory of a Geological Map, together with the first geological map of that country. Maclure's 1809 Geological Map antedates William Smith's geological map of England and Wales (with part of Scotland) by six years, although it was constructed using a different classification of rocks.

The first major US diplomat to Latin American was Thomas Sumter, Jr., who was sent to the the Portuguese court in exile in Brazil.  He was assigned there for two main reasons: send back details on the natural resources and products of the country and negotiate a political arrangement.  He was first hand witness to great events in South America, including the start of the wars for independence. He communicated with the American commissioners at Ghent negotiating to end the War of 1812, and with the State Department.  He was the most senior representative of the American government south of the Equator.

Sumter’s father was a hero of the Revolutionary War but was also close to William Maclure.  Maclure knew the son well.

Around 1815, Sumter, engaged as he was in surveying the natural and commercial resources of Brazil, commissioned a study of the geological products of the regions and operations in and around Rio de Janeiro.  These he sent to the US Ambassador to France, William H. Crawford, with a note that they were “for Mr. Maclure [who was in Europe] This map shows the sea level, and contours of the land in the Bay. It shows mineral deposits (sandstone and granite, for example) and gives their location.  It also shows the diamond district of serra do trio. The Portuguese government claimed the stones as crown property, and marked out a definitely bounded diamantiferous district, called the Serro do Frio district, which was to be under its own control, and subject to special laws and regulations preventing the ingress of unlicensed diamond-seekers, while a strict military supervision forbad any dishonesty among the workers". This was the first diamond mine in the Americas and for a long time the only place in the Americas where diamonds were found.

In all the survey lists nearly 100 locations throughout the explored and populated portion of Brazil. Sumter communicated with Crawford, and sent him this map, writing himself on the outside “For Mr. Maclure.”