Laser technology maps size of ancient gold excavations in SP

Using lasers that pass through the vegetation, the Archeology Center of São Paulo (CASP) managed to map the size of one of the excavations from where it was extracted gold in the capital of São Paulo. The pit, located in Jaraguá, north of São Paulo, must have been in operation during the 18th and 19th centuries. But the history of gold mining at the site is even older. In 1562, the first deposits of gold of Brazil.

• The so-called caves are difficult to identify because most of them are covered by forests. But the laser beams made it possible to map the terrain in three dimensions and form a 3D image of the area.
• The pits are difficult to occupy to this day because they are quite steep. The models built using the new technology were able to accurately identify that the holes are 20 meters deep and 100 meters long.

According to CASP geologist, Francisco Adrião Neves da Silva, mapping is important to help visualize the area. The geologist explains that, through an aerial view or walking across the land, it is not possible to get an idea of ​​the dimensions of the pit. “We did 3D printing precisely so people could hold it in their hand and look, give an idea of ​​the size and know that it actually exists,” he says.

The model was created in 2019, shortly after São Paulo City Hall made the technology available to collect data from the municipality.

The Municipal Council for the Preservation of Historical, Cultural and Environmental Heritage of the City of São Paulo (CONPRESP) listed the four historic gold exploration pits in Jaraguá in 2012, following a report on the structures. 3D mapping was also published online.

Mining past

By a letter of 1562, the king of Portugal and Brazil received the news that in the current State of São Paulo, near Jaraguá, there would be gold. The news came even before the discovery of the State of Minas Gerais, where there was a large part of Brazilian mining. From then on, people from São Paulo went on expeditions in search of more gold.

The region began to be explored in 1600 on the banks of the river, with so-called alluvial gold. The geologist says that the pits were built later, when the ore on the edges had already been exhausted. These structures were widely used in mining of Minas Gerais, where gold is removed from the ground on slopes. The technique later reached São Paulo.

Francisco Adrião states that the slopes represent the last phases of gold exploration in Jaraguá, when exploration returned to the state of São Paulo, as gold production had declined in Minas Gerais.

Other evidence of gold exploration in Jaraguá are structures identified as gold tanks. These are stone masonry boxes intended for washing ore. These structures are located in the Guarani indigenous reserve.