Verneuil’s rubies

When a colleague suggested the minerals gallery at the Natural History Museum for a field trip it seemed a no-brainer: the range of materials and crystals would suffice to inspire the most jaded of students. While there, I paused by a case of synthetic crystals marvelling at a rod, opaque at one end, before narrowing down to a narrow neck and then swelling to a stunning deep red ball of ruby. The label pronounced the crystals were ‘grown by the Verneuil process’. I had no idea what that was – and promised my students I would find out.