The following photographers have kindly supplied illustrations: W.A.M. Devile, Rijks-museum van Geologie en Mineralogie, Leiden, The Netherlands: W Lieber, Heidelberg, Germany; J, Weber, Mamaroneck, U.S.A. Part ol the pictures by W.A.M. Devile have appeared in the 25-volume "Grote Winckler Prins Encyclopedie" !8th, completely revised edition, 1980), published by B.V. Uitgeversmaatschappij Elsevier, Amsterdam. They are reprinted with permission. Part of the pictures by W. Lieber have been printed in his book "Bunte Welt der schonen Steine" (4th edition, 1978) published by Franckh-Kosmos Verlagsgruppe, Stuttgart, Germany. They are reprinted with permission. Cooperation of B.V. Uitgeverij en Boekhandel W.J. Thieme & Cie, Zutphen, The Netherlands is greatfully acknowledged. J.H. Puffer, Newark, U.S.A., kindly supplied data for the section of the index dealing with hazardous properties. © Elsevier Science Publishers B.V., 1983. 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, wifhout the prior written permission of the publisher, Elsevier Science Publishers B.V., P.O. Box 330, 1000 AH Amsterdam, The Netherlands.
