Originally published in 1937, this book deals primarily with precious stones as mineral products and is written from a mineralogical point of view. It gives a background to the principles of mineralogy and uses technical terms, but aims to put these into popular language, making this an easy to use guide. Contents Include: GENERAL PRINCIPLES: Introduction Colour, Lustre and Brilliancy Density and Hardness, Heaviness and Durability Forms of Crystals Optical characters of Precious Stones, Their Action on Light Chemical Composition: What Precious Stones are Made of Geological Occurrence and Origin of Precious Stones Mining of Precious Stones Cutting and Polishing Gems: Forms of Cutting Imitation Gems and Artificial Gem-Stones . Nomenclature of Gems: Names of Gem-Stones and Minerals DESCRIPTIVE PORTION: Diamond - Corundum and it's Colour Varieties, Ruby and Sapphire - Spinel and Chrysoberyl - Beryl and Topaz The Garnet and Tourmaline Groups - Zircon and Olivine - The Quartz Group - Opal and Silica-Glass - Jade (Nephrite and Jadeite) - Lapis-Lazuli and Turquoise. Miscellaneous Gem-Stones - Gem Materials of Organic Origin: Amber, Jet, Pearls, Coral. Это и многое другое вы найдете в книге A Key to Precious Stones (L. J. Spencer)