Manuel-Mercedes open pit

The Manuel-Mercedes open pit is located in the Cala Mines, within the municipality of Cala, Huelva province, Andalusia, Spain, at approximately 37° N, 6° W, and an altitude of 586 meters. It sits in the Sierra de Aracena, part of the western Sierra Morena range, near the border with Extremadura. This area is known for its mountainous terrain and is close to other notable mining sites, such as the Rio Tinto mines, famous for their long mining history.

This locality is a treasure trove for mineral enthusiasts, featuring a diverse range of minerals. Uncommon finds include annabergite, gersdorffite, nickelskutterudite, and skutterudite, which are particularly sought after for their rarity. Common minerals like quartz, pyrite, azurite, malachite, and chalcopyrite are also abundant, offering a rich variety for collectors and researchers.

The geological setting is fascinating, with the deposit located on the southern flank of the Olivenza-Monesterio antiform within the Ossa-Morena zone. It consists of Palaeozoic rocks affected by Hercynian tectonics, featuring granitic intrusions that led to contact metamorphism. This process formed skarns, rich in magnetite, which are key to the mineral diversity found here, resulting from hydrothermal activity and metamorphic processes.

Mining at Cala Mines dates back to Carthaginian times, highlighting its ancient roots. The 19th century saw a resurgence with foreign companies, including British and German firms, extracting copper, iron, and gold, supported by a railway to San Juan de Aznalfarache. In 1982, facing closure, 20 miners locked themselves in a gallery, prompting a political promise from Felipe Gonzalez to keep the mines open, which he fulfilled after winning elections. The mines were managed by PRESUR until their final closure in 2010, leaving a legacy of industrial heritage.

Cala's culture is deeply tied to its mining past, with landmarks like the Castillo de Cala (a 12th-14th century fortress) and the Ermita de Nuestra Señora de Cala reflecting its historical significance. The town celebrates the Romería de San Roque in May, a vibrant procession with horses and carts, showcasing local traditions. Gastronomically, it's famous for Iberian ham from the dehesa, with dishes like caldereta and sweets like perrunillas, rooted in the region's oak forest landscape.

The climate is Mediterranean, with hot, dry summers and mild, wet winters, cooler than coastal areas due to its inland, higher altitude location. Average temperatures range from 10°C high and 0°C low in January to 30°C high and 15°C low in August, with winter-spring precipitation around 50-100 mm/month. Ecologically, it's part of the Sierra de Aracena and Picos de Aroche Natural Park, featuring oak, cork oak, and chestnut forests, supporting biodiversity like wild boar and birds, and the dehesa ecosystem for Iberian pig farming.