Color encyclopedia of gemstones

332 Pages·2013·52.62 MB·English

by  Arem, Joel E

SECOND
EDITION
COLOR
OF
NCYCLOPED1A
E
JOEL AREM, PHD,
FG.A.
'
COLOR
iNCYCLOPEDIA
SECOND EDITION
JOEL E. AREM, PH.D., FG.A.
Since 1977, gemologists, gem collectors,
jewelers, and gem dealers have relied on
this acclaimed sourcebook for immediate
access to essential information on gems.
Now fully updated and revised, Color En-
cyclopedia ofGemstones, SecondEdition, is the
most complete and comprehensive tabula-
tion ever available on the properties of all
known gemstone species and varieties.
With speed and convenience, the Encyclo-
pedia will direct you to concise and accurate
data on a particular gemstone's physical
properties, occurrence, chemistry, avail-
ability, rarity, and market potential. And
the book's spectacular full-color photo-
— —
graphs over 300 in all illustrate many
gems that are depicted in no other
gemstone book.
A major feature of this second edition is
the new coverage ofsynthetic gems. In this
section you will find complete data on all
the important synthetic materials, includ-
ing those with and without natural counter-
parts. There is also information o—n some
of the more unusual synthetics some
hardly ever encountered as cut gems and
therefore posing serious identification prob-
lems. And the introductory material to this
section clarifies for the first time in print
the true definitions of "synthetic" and
"homocreate" materials, bringing gemology
into line with internationally accepted
nomenclature standards. Diagrams of the
important crystal growth methods and de-
scriptions of how they work round out the
wealth of coverage on synthetics available
to you here.
Also of special interest, and new to this
edition, is a detailed analysis of color and
color measurement as applied to gem-
stones. Here the author presents a com-
prehensive listing of machine-generated
(Continued •> <,\kflap)
A VAN NOSTRAND REINHOLD BOOK
SAUSALITO PUBLIC LIBRARY
3 1111 01084 102
For Reference
Not to be taken from this room

COLOR
ENCYCLOPEDIA OF
GEMSTONES

COLOR
ENCYCLOPEDIA OF
GEMSTONES
Second Edition
EGA.
Arem,
Joel E. Ph.D.,
VAN NOSTRAND REINHOLD COMPANY
VHE
New York
Sausalito Public Library
c i:*~ r~\:t*~*\~ Oaoas
This book is dedicated to Abraham "Edge" Goldstein of Brooklyn,
New York. His love of minerals and gems and his generosity and
willingnesstoshare hisknowledgewithothershave been an inspira-
tion to three generations of hobbyists. I consider myself fortunate
to be numbered among thosewhom Edgeconsidershisclose friends.
Copyright © 1977, 1987 by Van Mostrand Reinhold Company Inc.
All photographscopyright © 1977, 1987 by Joel E. Arem
Library ofCongress Catalog Card Number: 86-26759
ISBN: 0-442-20833-2
All rights reserved. No part of this work covered by the
copyright hereon may be reproduced or used in any form or
by any means—graphic, electronic, or mechanical, including
photocopying, recording, taping, or information storage and
retrieval systems—without written permission of the publisher.
Printed in the United Statesof America
Van Nostrand Reinhold Company Inc.
115 Fifth Avenue
New York, New York 10003
Van Nostrand Reinhold Company Limited
Molly Millars Lane
Wokingham, Berkshire RG11 2PY, England
Van Nostrand Reinhold
480 La Trobe Street
Melbourne, Victoria 3000, Australia
Macmillan ofCanada
Division of Canada Publishing Corporation
164 Commander Boulevard
Agincourt, Ontario MIS 3C7, Canada
16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
Library of Congress Cataloging-in-Publication Data
Arem,Joel E., 1943-
Color encyclopedia ofgemstones.
Bibliography: p.
Includes index.
1. Precious stones. I. Title.
QE392.A69 1987 553.8 '03 '21 86-26759
ISBN 0-442-20833-2
Contents
Preface I vi
Acknowledgment I viii
INTRODUCTION / 1 GEM SECTION / 37
What Is a Gem? / 2
Scope of This Book / 3 GEMSTONES FROM THE LABORATORY / 211
The Nature of Gems / 4 History / 211
Crystal Structures and Properties / 4 Crystal Growth / 212
Origin of Gemstones / 6 Definitions / 217
Rock Classification / 6 Characteristics / 218
Gem Scarcity / 8 Synthetic Gem Listing / 220
Rock Types / 9
Igneous Rocks / 9 HOMOCREATE MATERIALS THAT HAVE
Intrusive / 9 BEEN SYNTHESIZED / 232
Extrusive / 9
SSeeddiimmeennttaarryy RFeoactkusres/ /9 10 TRADE NAMES OF SYNTHETICS / 233
Metamorphic Rocks / 10
Identification of Gemstones / 10 BIBLIOGRAPHY / 236
General / 236
SOURCES OF DATA USED IN TEXT / 13 Jewelry / 236
Formula / 13 Diamonds / 237
Crystallography / 13 Specific Gemstones / 237
Color / 14 Mineralogy / 237
Luster / 14 Synthetics / 238
Hardness / 14 Journals / 238
Density / 15
Cleavage / 16 GEMSTONE SPECIES AND
Optics / 16 ORNAMENTAL MATERIALS / 239
Spectral / 18
Inclusions / 19 MINERAL GROUPS OF GEMOLOGICAL
Luminescence / 19 INTEREST / 241
Occurrence / 19
CStoomnmeeSnitzess // 2109 REFRACTIVE INDEX GRAPH / 242
THERMAL PROPERTIES PERIODIC CLASSIFICATION OF
/ 21
THE ELEMENTS / 243
COLOR MEASUREMENT AND
SPECIFICATION / 25 INDEX / 244
Preface
The first edition of this encyclopedia was published a deposits, including some extraordinary pink material.
decadeago,andsomeremarkablechangeshaveoccurred So-calledfancycoloreddiamonds(in truth,coloredgem-
inthegemstonemarketplaceduringthisinterval.Although stones) may well become the most eagerly sought and
diamond still retains its place as the most popular and highly prized of all gems before the next edition of this
esteemed of all gemstones, the extremely wide gap in book is published.
this leadership position versus colored stones has nar- The growing popularity of colored gemstones has
rowed.There isalargeandgrowingdemandforall kinds made itcrucial thatasensible,scientific,precise,consis-
ofgemstones,especiallybrightlycoloredstonesthatcan tent, and universally accepted method of color grading
bewornasfashionaccessories.Beadedjewelryhasbecome be developed. The immense pool of capital in pension
an item of immense popularity; pearls have seen a huge plansandtrustaccountswill nevertouchgemsaswealth-
revival. Rare gemstones such as tanzanite and tsavorite preservation vehicles untilsuchgradingisanestablished
have made the transition from collector items to market fact. Many grading systems have been proposed. All of
staples. Even such barely commercial stones as andalu- them, without exception, have the same basic failing,
site, iolite, sphene, chrysoberyl, and some of the feld- thatis,despitethepseudo-scientificappearanceof"num-
sparsare becoming morewidely known and distributed. ber systems" for estimating color, clarity, cut, and so
The long-speculated and long-awaited birth ofalargeand forth, theyare all basedon visualestimation. Thisisalso
active collector market for gemstones cannot be far off. true of diamond, an amazing fact considering that a
Aboutthirtynewspeciesmaynow beaddedtothelist multimilliondollarinvestmentmarket roseandfell based
of cut gems, along with some new varieties, such as on "certification' with a built-in variability as high as
malayagarnet.Previouslyunknownlocalitieshaveyielded 20-30percent. Large money poolswill neverbe invested
large and spectacular crystals of rare species, such as in any product that must be defined in such loose terms,
anglesite,which in turn have yielded record-size faceted with the consequent potential for immediate loss on
gemstones. More and more dealers are aware of the liquidation as large as the upper end of the range of
growing value of exotic gem species; the list of known grading error.
taaffeites has thus grown from a handful ofgems to per- Onlyobjective,scientific,machine-basedgradingwill
haps more than fifty known cut stones, and more will solve this problem. This implies the acceptance by the
surely be identified. gemstone field ofterminology that isuniversally applied
On the commercial side, the Argyle deposits of Aus- inotherindustrieswherecolorisequallyimportant(paints,
tralia have become the most important diamonddiscov- textiles, plastics), such as Munsell color designations.
eriesofthe century, adding asmuch as 50 percent to the Also, the variability of color grading by such machines
provenworldreserveofdiamond.Unfortunately,mostof must be reduced to less than 5 percent, a formidable
the Australian diamonds are not suitable for cutting as challenge indeed considering the complexityofmeasur-
gems, so while the amount ofdiamond in these deposits ing color in materials where pleochroism, cutting pro-
is immense, the total value is not as large as might be portions,andinclusion-scatteringareall potentialsources
guessed. However, there seems to be an unusually high of error.
percentageofbrightlycoloreddiamond in theAustralian The gemstone field is also continually searching for
VI