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: βHow to Use this Bookβ, βRefractive Index and its Measurementsβ, βDouble Refraction and How to Detect Itβ, βColour, Colour Filters and Dichroscopeβ, βThe Specific Gravity of Gem-Stones and How to Measure Itβ, βDetection of Synthetic and Imitation Stonesβ, βThe Use of the Microscopeβ, etcetera. This antiquarian book is being republished now in an affordable, modern edition - complete with a specially commissioned new introduction on gemmology.