Roger is a scientist whose main career was in health and safety management but his original degrees were in Colour Chemistry. In his retirement he has developed an interest in minerals which has led to this series of talks. The first: ”A Kaleidoscope of Chemical Colour” looked at how spectacular colours could be obtained using a polarising microscope and crystals from minerals and other sources; the second: “Lava & Lime” looked at the use of lime in plaster, mortars and cements but also mentioned “Limelight”; this the third will continue to look at “Limelight” and other types of Luminescence. This is an online event.