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: âHow to Use this Bookâ, âRefractive Index and its Measurementsâ, âDouble Refraction and How to Detect Itâ, âColour, Colour Filters and Dichroscopeâ, âThe Specific Gravity of Gem-Stones and How to Measure Itâ, âDetection of Synthetic and Imitation Stonesâ, âThe Use of the Microscopeâ, etcetera. This antiquarian book is being republished now in an affordable, modern edition - complete with a specially commissioned new introduction on gemmology.