3/6. How has the geology of the planet influenced the history of art? As Dr lain Stewart provides a geologist's insight into some familiar sites of artistic interest, he shows how early cave painters began by scraping pigments from the rocks, while the Egyptians and Arabs developed ingenious transformation techniques that broadened their colour palettes dramatically. He brings the story up to date by demonstrating how an ever-advancing understanding of rocks continues to increasing their potential for painters. Producer Nikki Melluish ; Series producers Belinda Cherrington and Jeremy Phillips First shown on BBC4