The Cruzeiro Mine: A Treasure Trove of Tourmaline in Brazil

Nestled in the lush green landscape of Minas Gerais, Brazil, the Cruzeiro Mine stands as a testament to nature's extraordinary ability to create beauty. This world-renowned mine has been producing some of the finest tourmalines for decades, captivating gem enthusiasts and collectors alike with its remarkable variety and quality.

Location and History

The Cruzeiro Mine is located about 36 miles northwest of Governador Valadares in Minas Gerais state, Brazil. Situated atop the Serra Resplendecente do Cruzeiro mountain at an elevation of 4,593 feet, the mine offers a spectacular view of the surrounding hills and verdant landscape.  Mining operations at Cruzeiro began around 1915, initially focusing on mica production. The mine played a significant role during World War II as a major mica supplier. However, it wasn't until the 1950s that the mine's true gemstone potential was realized, and tourmaline became the primary focus of extraction

Geological Marvel

The Cruzeiro Mine is renowned for its enormous pegmatites, which are the source of its exceptional tourmaline crystals. These pegmatites are truly massive, with some measuring 32 meters wide and over one kilometer in length.  This extensive pegmatite formation provides an ideal environment for tourmaline crystallization, contributing to the mine's prolific production.

Tourmaline Variety

One of the most remarkable aspects of the Cruzeiro Mine is the incredible variety of tourmaline it produces. The mine yields tourmalines in all colors, making it a veritable rainbow of gemstones. Here's a breakdown of the color distribution:

• Green: Makes up the largest percentage of total production
• Pink and Rubellite: Comprise about 30% of production
• Blue: Accounts for approximately 10% of production

The mine is also famous for producing bicolored and multicolored crystals. It's common to find crystals that transition from pink or rubellite colors to green, often terminating in black. This color zoning creates the popular "watermelon" tourmalines, which are highly sought after by collectors and jewelry designers.

Mining and Production

The mining operation at Cruzeiro is both extensive and meticulous. The mine features an array of horizontal tunnels, or galleries, at different depths, with some extending up to 500 meters. Miners evaluate pegmatites by examining the central quartz core zone, where they typically find green tourmaline at the side contact areas. Tourmaline crystals are often found scattered throughout the walls of the pegmatites in a pattern called "staining," or concentrated in pockets. The extraction process is largely done by hand, using picks and other hand tools to carefully remove the crystals from the surrounding rock.Annual production at the Cruzeiro Mine is impressive. Of the estimated eight tons produced annually:

• 70% is carving and bead quality
• 10% is clean facet grade
• 10% is cabochon grade
• 10% is suitable for mineral specimens

Famous Finds

The Cruzeiro Mine has a history of producing exceptional specimens and large quantities of tourmaline. Some notable finds include:

• In 1966, a single 14-kg deep red rubellite crystal was discovered, which yielded 10,000-12,000 carats of very clean stones.
• In 1968, over 2,000 kilos of largely opaque crystals of fine green color were removed from a single pocket.

Unique Characteristics

What sets Cruzeiro tourmalines apart is not just their variety, but also their quality. The gems cut from blue and green material are often eye-clean, a highly desirable trait in gemstones. The mine has produced some of the finest red tourmalines (rubellites) ever found in Brazil, with crystals reaching 5 cm or more in length.

Rarity and Value

While green, pink, and blue tourmalines are more common at Cruzeiro, the mine occasionally produces rarer colors. For instance, a recent auction featured a rare silvery-purple tourmaline from Cruzeiro, showcasing the mine's potential for producing unexpected and highly valuable specimens.

Conclusion

The Cruzeiro Mine continues to be one of the most important and consistent sources of high-quality tourmaline in the world. Its rich history, geological uniqueness, and the sheer variety and quality of its production make it a true gem in the world of mineralogy and gemology. For anyone interested in the beauty and diversity of tourmaline, the Cruzeiro Mine remains an endless source of fascination and wonder.