Lectures given by James Geikie on mineralogy, covering areas including the form of minerals (crystals), their characteristics depending on light (colour, pleochromism, play of colours, iridescence, lustre, transparency, refraction, phosphorescence), characters depending on state of aggregation (hardness, tenacity, fracture), other characteristics (taste, odour, feel, electricity, magnetism, specific gravity) and their origins (solution, fusion, sublimation).