Gems of the world

Cally Oldershaw

Book - 2008

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Subjects
Published
Buffalo, N.Y. : Firefly Books 2008.
Language
English
Main Author
Cally Oldershaw (-)
Physical Description
256 pages : illustrations (chiefly color), color maps ; 26 cm
Bibliography
Includes index.
ISBN
9781554073672
  • Foreword
  • Introduction
  • Gem Formation
  • Mining
  • The Diamond Industry
  • Diamond Cutting and Trading Centers
  • Conflict Diamonds -- Ethical Sourcing
  • Crystal Structure
  • Optical Properties
  • Physical Properties
  • Fashioning and Cutting
  • Gemstone Cuts for Diamonds
  • Buying a Diamond
  • Buying Colored Gemstones
  • Imitation and Synthetic Gemstones
  • Gemstone Enhancement
  • History of Gems
  • Famous Diamonds
  • Caring for Gemstones and Jewelry
  • Color Key
  • Classification
  • Gems
  • [illustrated descriptions of varieties of gemstones grouped as:]
  • Carbon (diamond)
  • Sulfides (3 gems)
  • Oxides and Hydroxides (12 gems)
  • Halides (flurorite)
  • Carbonates (9 gems)
  • Borate (sinhalite)
  • Sulfates and Chromates (4 gems)
  • Tungstate (scheelite)
  • Phosphates (5 gems)
  • Silicates (87 gems)
  • Igneous Rock (obsidian)
  • Tektites (moldavite)
  • Synthetics and Imitations
  • Organics (7 types)
  • Precious Metals (3 types)
  • Important Gem Locations of the World
  • Glossary
  • Index
  • Useful Addresses and Acknowledgements
Review by Booklist Review

Internationally renowned mineralogist, expert gemologist, and former curator of gemstones Oldershaw has written a wonderful reference guide to the field of gemology. In the lengthy introduction, she moves from basic explanations of various types of rocks and minerals to geodes, the formation of crystals, and the characteristics of precious and semiprecious gemstones. Even color formation is discussed and illustrated. We learn the differences between naturally and synthetically formed gems and ways of identifying the imitations, fakes, and forgeries. Skills of lapidary artisans, jewelers, and jewelry designers are referred to when discussing qualities of gemstones their durability, clarity, surface types, etc. Advice is given on gem cutting, polishing, use of settings, general care, and cleaning. A large segment of the 70-page introduction is devoted to the diamond industry. Following the introduction, an illustrated color key groups more than 130 varieties of precious and semiprecious stones into 8 color categories yellow to brown, red to pink, blue to violet, green, colorless, white, black, and iridescent. In the gem description section, gems are arranged by chemical-composition classification. Each description includes color illustrations of rough and polished stones, various cuts (where appropriate), a specification chart, and prevalent locations throughout the world. The volume concludes with a series of world maps showing important gem locations. Comprehensive (though not all-inclusive) and lavishly illustrated, Gems of the World is intended for anyone who has ever been fascinated by crystals, jewelry, and gems, from general readers to seasoned professionals. It is a fine addition to general collections.--Cohen, Ann Copyright 2008 Booklist

From Booklist, Copyright (c) American Library Association. Used with permission.

Foreword We use the word "gem" in everyday language, for example "she is a real gem" and "this book is a little gem." In this context a gem is something special, highly valued and well-thought of, something to he treasured, with special attributes. Gemstones are also treasures. Their unique qualities have been valued throughout the ages, across continents and by different peoples, from our earliest ancestors to the present-day. It may have been the color or the crystal shape of a gemstone. or a brightly colored shell that first attracted the attention of someone who then bent down to pick it up. Something special about it would have encouraged that person to keep it, to own it, maybe to put it in a special place such as a bag hung around the neck, for safekeeping, to polish or make a hole in it, or to tie it on to clothing as an adornment or as a piece of jewelry. Gems and jewels are associated with the rich and famous. We may admire the jewels worn by our favorite film star, celebrity, or sportsperson. We may even aspire to own some particularly fine piece ourselves. Gems have been worn as a symbol of status, adorning the crowns of royalty -- a visual reminder of wealth, success and achievement to both the wearer and the observer. The power and energy ascribed to certain gemstones are an attribute defined by mystics and healers. The tales of famous stones, the luck they may hold or the curse they may inflict, can captivate an audience. In choosing this book, you may already have been captivated by the "specialness" of gemstones, or you may be interested in knowing more about them, you may work with gemstones, for example, as a scientist, a student, a designer, or a jeweler. Whether you are a scientist, an artist, or just interested, we hope that this book inspires and informs you. It is intended as a guide to the beautiful and fascinating world of gemstones. It shows you the glorious diversity of colors and the incredible crystal shapes Of these wonders of the natural world. There is information about the optical and physical properties of the gemstones, where and how they are found, how they can be worked and how they should be cared for. CRYSTALS AND GEMSTONES Some crystals look as fragile as glass and are incredibly rare, but they have an inherent strength. Crystals may take millions of years to form, or may form as you watch. They may have been formed in rocks deep beneath the Earth's surface, or they may be survivors of mountain-building episodes or devastating volcanic eruptions, or they may have been washed into rivers and streams to be retrieved maybe millions of years after their formation. These survivors are nature's treat: perfect and brightly colored crystals formed in dark, deep rocks. Generally speaking, gemstones are minerals that have formed as sufficiently clear, large crystals that can be cut and polished for use as pieces for personal adornment or objects d'art such as sculptures, inlays, and so on. Pre-cut gemstones and minerals in matrix are also collectable. In addition to the mineral gemstones there are also other materials that can be used for adornment such as pearl, shell, amber and other derivatives of plants or animals. These are called organic gems. WORKING WITH GEMSTONES But for a gemologist (someone who studies the science of gemstones, their physical and optical properties and their origins) or a jeweler, what are the special attributes of gemstones? For gemstones to be used in jewelry. ideally they should have three main attributes: beauty. durability, and rarity. Beauty and rarity have a direct impact on the value of a gemstone, the more beautiful and rare the greater the value. The color and clarity of a gemstone are just two of the aspects that a gemologist or jeweler will take into account when studying a gemstone or choosing the best gem material for jewelry. Durability, the strength of the gemstone. will affect how it can be worked, cut and set or mounted, and how it should be cared for to avoid it becoming scratched, cracked, or otherwise damaged. However, not all gemstones possess all three. For example. some may be insufficiently durable to use as a cut gemstone in a ring. but may be good as a piece within a brooch, protected from damage by the mounting. Some materials are best suited for fashioning as beads or cut en cabochon (with a domed surface), others look their best when faceted (fashioned with a number of flat, polished surfaces). The skill of the lapidary, jeweler or jewelry designer lies in their ability to recognize the qualities of the gem materials, working with them to their best abilities to produce a piece that is both admired and sought after. They will need to find the best compromise between what is possible and what is practical. Jewelers also need to understand the strengths and weaknesses of various gem materials in order that they can be confident of the identity of the material they are trading and also so that they can advise the customer on the best care and cleaning methods, and most importantly disclose any treatments, for example oiling or heating, which may affect the value, use, or durability of the article. IMITATIONS, FAKES, AND FORGERIES Not all gemstones are what they seem. A gemstone that has similar properties to a more valuable or rare specimen may be used to imitate it. Color can be misleading: for example, the color of a red spinel might be mistaken for a ruby. Glass. plastic and other materials both natural and manmade can also be used to imitate gemstones.Even the assumption that a gemstone has been formed naturally may not be true. Synthetic gemstones have the same chemical and physical properties as their natural equivalent, but they are made in the laboratory. Part of the excitement of being a gemologist is to know how to use your eyes and the various pieces of equipment available in order to distinguish the imitations, fakes, and forgeries from the real gems. Excerpted from Gems of the World by Cally Oldershaw All rights reserved by the original copyright owners. Excerpts are provided for display purposes only and may not be reproduced, reprinted or distributed without the written permission of the publisher.