The North Pennines is world-famous for its remarkable mineral veins and deposits, known collectively as the Northern Pennine Orefield. Mining for these minerals has had a profound effect on the landscape.
How the mineral veins formed
The veins of lead ore and other minerals formed about 290 million years ago. Hot mineral-rich waters, heated by the buried Weardale Granite, flowed through cracks and fissures deep underground. As the fluids cooled, the dissolved minerals crystallized within the cracks, forming mineral veins. Sometimes the fluids reacted with limestone on the sides of the cracks, altering the rock and forming mineral deposits known as ‘flats’.
Some of the world’s finest and most spectacular specimens of minerals such as fluorite, witherite, barytocalcite and alstonite have come from the North Pennines. Examples of these minerals can be found in most of the world’s major mineralogical collections. Visit Killhope, the North of England Lead Mining Museum to see some superb specimens of the area’s minerals.
Mining for lead ore in the North Pennines probably goes back at least 2,000 years. The industry had its heyday in the 19th century, but by the mid 20th century the last few lead mines had closed. Other commercially mined minerals include sphalerite (zinc ore), iron ores, fluorite (also known as fluorspar) and barium minerals such as baryte and witherite. Everywhere you look in the North Pennines you’ll see the legacy of mining – from spoil heaps, mine shafts and chimneys to the area’s pattern of settlements and distinctive ‘miner-farmer’ landscapes of isolated smallholdings.
Research and discovery
The North Pennines has a long history of research on mineral deposits. Ideas and concepts developed here by miners and mine managers, and later by geologists and mineralogists, have been fundamental to the understanding of mineral deposits around the world. Several minerals – witherite, barytocalcite, alstonite and brianyoungite – were first recognised in the North Pennines.