PREFACE 



Tnii desire of the publishers to present, to the German pubHc, a work on precious stones 

 similar in character to that admirably supplied in American literature by George 

 Frederick Kunz's " Gems and Precious Stones of North America "" gave the initiative to the 

 writing of the present book. In this case, however, all precious stones had to be dealt with, 

 and an introduction to the methods employed in their determination had also to be given. 

 Tor the latter the excellent and exhaustive instructions given by C. Doelter in his 

 " Edelsteinkunde " may serve as a model. These, however, have been somewhat modified 

 and simplified. In particular the examination in convergent polarised light has been 

 dispensed with, since it is unusual for gem-merchants and jewellers to be sufficiently well 

 acquainted with the theory of the subject to make practical use of this method, while 

 information of this description would be superfluous to a trained mineralogist. It has been 

 considered advisable, however, to preface the systematic description of precious stones with 

 a general survey of the related sciences, especially those of physics and mineralogy, in so 

 far as they assist in the understanding of the nature of precious stones. 



The reader is assumed to be neither a specialist in science nor wholly without scientific 

 knowledge. It has been sought to treat the subject in such a way that it may be intel- 

 ligible to any one possessed of a good general education. It is therefore hoped tha^t the 

 book will suffice for those who take a general scientific interest in precious stones, and 

 that it will be specially useful to those engaged in the buying and selling of precious stones 

 and in their application to purposes of ornament, namely, to gem-merchan+s and 

 jewellers. 



It ^^■as at first considered that pearls and coral, being not minerals but products of the 

 animal kingdom, could not properly find a place in this work. In deference, however, to the 

 \\ishes of the readers of the earlier parts of the book, an apjjcndix dealing with these 

 important subjects has been added. In writing the section on pearls, the works. of Mobius 

 and von Martens, among others, have been consulted, and for coral, those of Lacaze-Duthiers 

 and of Canestrini. 



The author has taken especial pains to treat of the mode of occurrence and the localities 

 of each stone \\ ith as much detail as the size of the volume allowed ; and the distribution of 

 stones in the most important of the countries in which they are found is graphically shown 

 by small sketch-maps in the text. Many new facts relating to this subject have been 

 connnunicated by the author's colleagues, but even the latest mineralogical literature shows 

 that inaccuracies still abound. Onl}' those who have themselves gone into this branch of 

 mineralogy and have realised how widely scattered are the accounts which deal with the 

 occurrence of precious stones, and how prevalent errors, uncertainties and mistakes are, can 



