Sphalerite with Siderite

specimen number:
2102264

location:
Force Crag Mine, Keswick, Cumbria, England, UK

description:
Lustrous sharp black crystals of sphalerite to 1.0 cm in size on matrix with crystallized siderite. In good condition with minimal cleaving all around the edges of the piece only.

The Force Crag Mine, situated at the head of the Coledale Valley near Keswick in the Lake District, was the last working metal mine in Cumbria. Geologically, the site is characterized by a major east-west mineral vein known as the Force Crag Lode, which cuts through the Ordovician-aged Skiddaw Group slates. This hydrothermal vein was primarily mineralized with zinc, lead, and barium ores, including sphalerite, galena, and massive baryte, often exhibiting complex multi-stage deposition. Historically, mining activity at Force Crag began in the early 1800s, with various periods of operation targeting lead first, then later zinc and baryte. The mine saw several phases of development under different companies, with notable activity in the 1860s and early 1900s, and it remained active intermittently through the mid-20th century. Final commercial operations were conducted by the New Coledale Mining Company until 1991, when a major roof collapse and falling metal prices led to its permanent closure. Today, the site is managed by the National Trust and is preserved as a Scheduled Ancient Monument, standing as a significant reminder of the regions industrial mining legacy.

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