This vintage book contains a complete guide to testing gems and gemstones for purity and authenticity. Complete with a plethora of useful illustrations and all the information a prospective or existing enthusiast might need to know about the subject, this book constitutes an ideal resource for anyone with an interest in lapidary and gem testing. The chapters of this volume include: "How to Use this Book", "Refractive Index and its Measurements", "Double Refraction and How to Detect It", "Colour, Colour Filters and Dichroscope", "The Specific Gravity of Gem-Stones and How to Measure It", "Detection of Synthetic and Imitation Stones", "The Use of the Microscope", etcetera. This antiquarian book is being republished now in an affordable, modern edition - complete with a specially commissioned new introduction on gemmology.