Torbernite

specimen number:
2072132

location:
Calo, Vimianzo, A Coruna, Galicia, Spain

description:
Attractive lustrous crystals of torbernite measuring to 0.3 cm in size across the top of a quartz matrix. In good condition. Neat locality example for the species.

The mining area of Cala, located near A Coruna in the Galicia region of northwestern Spain, is situated within the Hercynian basement of the Iberian Massif. Geologically, the mineralization is associated with late-Hercynian granitic intrusions that penetrated older metamorphic rocks, creating hydrothermal vein systems rich in uranium and other metals. These deposits formed as primary uranium minerals were deposited in fractures and subsequently underwent intense secondary oxidation due to the humid, temperate climate of the Galician coast. Historically, the region saw various periods of exploration and small-scale mining for radioactive ores during the mid-20th century, particularly under the supervision of Spanish national energy authorities. While many of the old workings are now overgrown or inaccessible, the district remains a significant locality in European mineralogy for the study of supergene uranium minerals formed in a granitic environment.

For mineral collectors, Cala is internationally famous for its exceptional torbernite specimens, which are considered some of the finest ever found in Spain. The torbernite occurs as a secondary mineral, typically forming as brilliant, emerald-green tabular crystals with a distinct micaceous or foliated habit. These crystals are renowned for their sharp geometric form and intense color, often appearing as "books" or square plates perched on a contrasting matrix of smoky quartz or weathered white feldspar. Unlike many other uranium secondary minerals that can be dull or earthy, the torbernite from this locality often displays a vitreous to pearly luster that makes it highly aesthetic. Because these specimens are radioactive, they require careful handling and storage, yet they remain highly prized by specialists for their vibrant saturation and their historical status as classic examples of the secondary mineralogy of the Iberian Peninsula.

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