2026

Brazil fieldwork in 2024

By Isabelle Beney, SSEF, first published in Facette 30 (March 2026)

Brazil is a historically famed source of gemstones, being a well known producer of various gem varieties – e.g., diamond, tourmaline, beryl and topaz. As such, it is a location of great interest to the SSEF for fieldwork initiatives and for collecting samples for further study. In November 2024, a brief but productive fieldtrip was carried out in Minas Gerais state, with the hope of better understanding the current emerald and imperial topaz mining activity in this area and collecting some new samples for analysis.

Figure 1: Imperial topaz in host rock at the Mina da Boa Vista. Photo: I. Beney, SSEF.

Imperial topaz mining

Imperial topaz is an almost uniquely Brazilian gem export nowadays, with the hub of mining being around the colonial town of Ouro Preto. In this area, there are a number of mines (both active and decommissioned), geographically aligned with the narrow subsurface geological structures linked to the formation of these gems. In this brief trip, the Mina do Capão (a.k.a., Capão do Lana) and the Mina da Boa Vista were visited, with both mines being situated just outside the town of Rodrigo Silva (just over 20 km by road from Ouro Preto). The Mina do Capão is a historic site which has produced imperial topaz for many decades, with records of activity in this area going back as early as the beginning of the 20th century. However, unlike the Mina da Boa Vista which still produces material, the Mina do Capão was decommissioned in 2018 and the old mine pit now hosts a lake (see Figure 2).

Figure 2: The decommissioned Mina do Capão, with the pit now inundated by a small lake. Photo: I. Beney, SSEF.
Figure 3: Imperial topaz gravel found in the road following rain in the town of Rodrigo Silva. Photo: I. Beney, SSEF.
Both mines are so-called ‘open pit’ sites, which means that all the mining activities are subaerial, rather than subterranean. This mining method is possible here due to the relatively shallow depth of the mineralised zone, and also the very weathered state of the host rocks. This means that they are soft and excavation requires comparatively few large pieces of machinery. It also means that the extraction of the imperial topaz from the host rocks is relatively easy. Samples were retrieved from both localities in the hope of conducting chemical analyses on them, and thus better constraining the nature and characteristics of this fascinating gem material.

Emerald mining

The second objective of this fieldtrip was to explore one of the currently smaller producers of high quality emerald material in the Itabira region. Emeralds are one of Brazil’s most prized mined exports, however, these stones can often show visual and chemical similarities to material from some African emerald sources. As such, it is important for the SSEF to remain up to date and constantly collect and test emerald samples from different sources so that we may better constrain origin.

Figure 4: Inside the Mina Canaã, observing classic ‘boudinage’ structures present in the veins cross cutting the host rocks. Photo: C. Santos (Mineração Canaã).

The impressively modern Mina Canaã equals the handful of other mechanised emerald mines world over, and it is one of the leaders in terms of health and safety within the realm of Brazilian subsurface mining. The mine has seen full time production since 2013, and although this is on a comparatively small scale, the mine has a reputation for producing some exceptional material (see article page 21 for a spotlight on some of the material from this mine that the SSEF has had the privilege of testing recently).

Figure 5: An emerald crystal within its host rock – a combination of phlogopite schist (darker areas) and felsic minerals, e.g., feldspar (lighter areas). Photo: I. Beney, SSEF.

Currently, the Mina Canaã has the infrastructure to process around 3000 tonnes of host rock (phlogopite schist – see Figure 5) per month, although this is set to double in the coming years with new developments to the site. These developments will also bring about the completion of the mine’s cutting and polishing facilities, with the hope that the highest quality mined material can be processed onsite in the future. In terms of tackling the questions of origin and traceability for Brazilian gems, this is a great place to start!

Figure 6: Looking down one of the tunnels inside the Mina Canaã during the visit. Photo: C. Santos (Mineração Canaã).

Acknowledgements

It was a huge pleasure to visit these mines and many thanks go to all those who made the site visits possible, namely Rafael Guerra, Odantes Machado, Adriano Mol, Cosme Santos, Jurgen Schnellrath and André Luis da Silva. Your time and hospitality were greatly appreciated, and the knowledge you imparted extremely helpful. Many thanks are also extended for the generous donation of samples to the SSEF collection, upon which further analyses will be conducted (see page 78 for more details on recent donations).