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Sue Nelson explores the mining town in North Carolina that is responsible for the production of the entire world's supply of silicon chips.
The small community of Spruce Pine is home to the purest quartz on Earth, which is essential for making the chips that run every computer, digital radio, washing machine and microwave on the planet.
Quartz is vital because of how computer chips are made; this uniquely pure mineral forms the mixing bowls and tools that make the manufacture of silicon chips possible. If the quartz is contaminated then it becomes useless, but by a stroke of geological luck these rocks formed in the shadow of the Blue Ridge Mountains are just perfect. Without them - and therefore without the work of this North Carolina town - microchip development as we know it would grind to a halt.
But as new quartz deposits are discovered in other countries, including Norway, could Spruce Pine cease to be indispensible? And what will the people of the town do if their last major industry disappears? The programme meets the locals of this Mitchell County town and digs beneath the surface of this strategically important mineral.