Man-Made Gemstones

199 Pages·1979·11.258 MB·English

by  Dennis Elwell

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MAN-MADE
H
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V GEMSTONES
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-I DENNIS ELWELL
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Frontispiece. A present fit for a Queen. Presentation made to H.M. Queen Elizabeth
by Dr. W. Bardsley on the occasion of her visit to the Royal Signals and Radar
Establishment, Malvern. Seven different materials grown in the laboratories
(Britain’s best known centre for crystal growth) are mounted in the form of a
flower with petals in the shape of radar dishes.
MAN-MADE
GEMSTONES
D. ELWELL
Center for Materials Research
Stanford University
111
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ELLIS HORWOOD LIMITED
Publishers Chichester
Halsted Press: a division of
JOHN WILEY & SONS
New York - Chichester - Brisbane - Toronto
First published in 1979 by
ELLIS HORWOOD LIMITED
Market Cross House, Cooper Street, Chichester, West Sussex, P019 1EB, England
The publisher's colophon is reproduced from James Gillison’s drawing of the
ancient Market Cross, Chichester
Distributors:
Australia, New Zealand, South-east Asia:
Jacaranda-Wiley Ltd., Jacaranda Press,
JOHN WILEY & SONS INC.,
G.P.O. Box 859, Brisbane, Queensland 40001, Australia.
Canada:
JOHN WILEY & SONS CANADA LIMITED
22 Worcester Road, Rexdale, Ontario, Canada.
Europe, Africa:
JOHN WILEY & SONS LIMITED
Baffins Lane, Chichester, West Sussex, England.
North and South America and the rest of the world:
HALSTED PRESS, a division of
JOHN WILEY & SONS
605 Third Avenue, New York, N.Y. 10016, U.S. A.
© 1979 Dennis Elwell/Ellis Horwood Ltd., Publishers Y;
British Library Cataloguing in Publication Data
Elwell, Dennis
Man-made gemstones.
1. Precious stones, Artificial
I. Title . a
666‘ .88 TP873 ^ ^ 78-41291
ISBN 0-85312-128-1 (Ellis Horwood Ltd., Publishers)
ISBN 0-470-26606-6 (Halsted Press)
Typeset in Press Roman by Ellis Horwood Ltd., Publishers
Printed in Great Britain by Cox & Wyman Ltd., Fakenham.
All rights reserved. No part of this publication may be reproduced, stored in a retrieval
system or transmitted, in any form or by any means, electronic, mechanical, photocopying,
recording or otherwise, without prior permission.
Table of Contents
Preface. 9
Acknowledgements.11
Introduction.13
Chapter 1 A Brief History
What is a Gemstone?.15
The early use of gems.18
The first man-made gemstones.20
Developments up to the Middle Ages.24
The 19 th Century.26
References.29
Chapter 2 Ruby, Sapphire and Spinel
Geneva rubies.32
Auguste Verneuil.34
Djeva.39
Star stones.47
Miscellaneous methods.49
References.55
Chapter 3 Emerald
The Espig process.59
Modern commercial manufacture.62
Hydrothermal emerald.66
Other methods.67
References.69
6 Table of Contents
Chapter 4 Diamond
Early attempts at synthesis. 73
The first success. 80
Gem diamond. 88
Direct transformation of graphite to diamond. 90
Growth under metastable conditions. 93
Diamond irradiation. 96
References. 98
Chapter 5 Diamond Substitutes
Properties of colourless gems.100
Rutile.102
Strontium titanate.105
Garnets.108
Cubic zirconia. 113
Yttrium aluminate.118
Yttrium oxide.119
Niobates. 119
Titanates.120
Bromellite.121
Magnesium oxide.121
Which is the best alternative to diamond?.122
References.123
Chapter 6 The Silica Family
Quartz.125
Opal.180
Slocum stone.139
References.141
Chapter 7 Other Synthetic Gemstones
Alexandrite.142
Coral.146
Lapis lazuli.180
Turquoise.182
References.184
Chapter 8 Synthetics of the Future
Natural stones.157
New gems from the scientific community.163
References.165
Table of Contents 7
Chapter 9 The Value of Gemstones
Gem testing.169
Standard testing procedures.170
Identification of synthetic gemstones.172
Gems as investments.176
References.176
Appendix 1
Properties of common gemstones.178
Appendix 2
Glossary of some specialised terms.179
Appendix 3
How to grow your own rubies.182
Appendix 4
Suppliers of man-made gemstones.187
Appendix 5
Bibliography.189
Index 190
This book is dedicated
to the memory of
my late father
Frank El well
Preface
This book is believed to be the first detailed account of the
manufacture of man-made gemstones. It was suggested because
there is no book dealing exclusively with the fascinating subject of
how man’s ingenuity can produce minerals which are as attractive as
the products of nature, and frequently even more so.
The approach adopted by the author is partly historical and
partly technological. The history of gem synthesis is considered an
important feature and three historical aspects - the early history of
faience and glass production, the development of the flame fusion
furnace and the saga of attempts to make diamond-are described
in detail. Modern methods of production are discussed in cases where
the details are known, but it must be remembered that the major
manufacturers often take considerable pains to safeguard the secrets
of their processes. Nevertheless it is felt that readers who study the
text should acquire sufficient information to be able to produce
attractive gemstones in their own laboratory, factory or workshop.
The impact of scientific research and development on the gem
scene has also been stressed at several points in the book. Science has
generated a large number of attractive new materials which have
greatly enhanced the choice of stones available to consumers. Usually
these new materials, from rutile to cubic zirconia, are by-products of
research in some totally unrelated field. In the fascinating example of
opal, research into the structure of the natural material made possible
the synthesis of gem opal, which was previously considered unlikely
or impossible.
The study of gem synthesis is a natural interest for a crystal
grower, because gems are the most attractive crystals grown - rather
it should be said that the most attractive crystals are inevitably
10 Preface
gemstones! This bock was mainly written for the sort of people to
whom the author has lectured over the years, especially amateur
lapidarists who are always keen to discover the ways by which man¬
made gemstones are produced, as well as to inquire about properties
and availability. The book should also be of interest to jewellers, who
must deal with synthetic gems in their profession, and to anyone,
technical or otherwise, seeking information on gems and their
production. The level of writing is approximately that of Scientific
American and no previous knowledge of the subject is assumed, but
references are included for those seeking further information.
The chapters are written as fairly independent units, with only
occasional cross-references. Chapter 1 is an account of the early
history of production of imitation gems, mainly in Egypt, with a
brief description of 19th century experiments which led eventually
to the gem crystal growth industry. In the second Chapter the
development of the first materials grown, corundums (such as ruby
and sapphire) and spinels, is described with reference to flame fusion
and to the range of more recent methods. Chapters 3-7 follow this
pattern, each Chapter being devoted to a material or group of
materials-emerald, diamond, the great variety of diamond simulants,
the quartz family and opal, and the recent coloured synthetics. In
each case the properties of the natural stone are considered so that
the question of whether the man-made material is a true synthetic or
not can be answered. Chapter 8 is a largely speculative account of
what the future has in store, while Chapter 9 is a brief review of gem
testing and factors governing the value of gems. Appendices contain
data tables and a glossary, a bibliography, data on gem availability
and a short introductory guide to ruby growth as a hobby.
This book was possible only with the help of a number of
colleagues, producers and other specialists who provided information
or illustrations. These are acknowledged in detail in the following
Section.
DENNIS ELWELL.
Stanford University,
June 1978.