Firefly Guide to Gems

by Oldershaw, Cally

• ISBN13: 9781552978146
• ISBN10: 1552978141
• Format: Paperback
• Copyright: 2009-01-01
• Publisher: Firefly Books Ltd

Summary

A reference guide to gems, semi-precious stones and crystals.Gemstones and crystals are used for jewelry, industry, lasers and precision technology. Firefly Guide to Gems is a practical, compact guide to the identification and use of precious and semi-precious stones, novelty stones, agates and crystals.An introduction explains geology, chemistry and gemstone properties in clear and accessible terms. Key aspects of gemstones are explained such as crystal structures and optical and physical properties.The first section of the book focuses on precious gems in their many forms, with illustrations of priceless jewelry. Practical information includes: Fashioning and cutting Types and shapes of cut Collecting Handling and storing gemstones Weighing and measuring stonesThe second and main section supplies complete descriptions of a wide range of gems, organized by chemical composition, for instance: Carbon (diamond) Aluminum oxide (saphire and ruby) Phosphate (turquoise) Silica (opal)A fascinating profile of each gem is accompanied with color photographs of the raw crystal, common cuts, and finally polished for use in jewelry. At-a-glance charts provide technical details such as refractive index, crystal group, luster, hardness and cleavage for each gem.Easy-to-read and abundantly illustrated, Firefly Guide to Gems is ideal for collectors and rockhounds.

Author Biography

Cally Oldershaw is a mineralogist and Liaison Officer for the Geological Society of London as well as an examiner for the Gemmological Association of Great Britain.

Table of Contents

Foreword	4	(2)
Introduction
Gem formation	6	(4)
Mining	10	(2)
Crystal structure	12	(4)
Optical properties	16	(4)
Physical properties	20	(4)
Fashioning and cutting	24	(4)
Imitation and synthetic stones	28	(3)
Enhancement	31	(1)
History of gems	32	(2)
Famous diamonds	34	(2)
Gemlore	36	(1)
Birthstones	37	(1)
Color key	38	(7)
Classification	45	(1)
GEMS	46	(165)
Maps of gem locations	211	(9)
Glossary	220	(1)
Useful addresses and acknowledgments	221	(1)
Index	222

Excerpts

ForewordWe often 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 be treasured, with special attributes.Gemstones are also treasures -- something special. 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 onto 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 mystic power and energy ascribed to certain gemstones are an attribute defined by 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. 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.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.But for a gemmologist (someone who studies the science of gemstones, their physical and optical properties and their origins), 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. However, not all gemstones possess all three. For example, some may be insufficiently durable (hard and tough) to use as a cut gemstone in a ring, but may be good for fashioning as a piece within a brooch, protected from damage by the mounting. Beauty and rarity have a direct impact on the value of a gemstone, the more beautiful and rare, the greater the price that will be paid.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 etc. Precut 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.But 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, at first glance the color of a red SPINEL might be mistaken for a RUBY. Glass, plastic and other materials both natural and man-made can also be used to imitate gemstones.Even