The scientists-turned-prospectors face their final challenge -to build a furnace that will turn their powdered gold flakes into solid nugget, from which they can make souvenirs of their six-week stay in New Zealand. With Kate Humble. Producer Martin Belderson ; Series producer Steve Evanson FREE BOOKLET: For a free Rough Science booklet and details of Open University programmes, call [number removed] or visit www.open2.net