INTRODUCTION 3 



Of the natural substances used for ornamental purposes other than precious stones, 

 pearls and coral are the most important. These, however, are not members of the mineral 

 kingdom, being products of animal life, and are therefore excluded in the consideration of 

 precious stones. Amber, on the other hand, though not a true mineral substance, finds a 

 place here. It is the fossilised resin of extinct trees, but being a constituent of the earth's 

 crust, as are precious stones, it is customary to regard it and similar substances as within 

 the domain of mineralogy. 



Since precious stones are minerals, their study must be considered as a branch of 

 mineralogy. It includes the investigation of their natural characters, such as chemical 

 composition, crystalline form, specific gravity, hardness, cleavage, and their behaviour 

 towards light, as well as an inquiry into their occurrence in the earth's crust, their mode of 

 origin there, and the localities where they are to be found. But since the application of 

 precious stones is a matter of practical importance, a thorough knowledge of the subject 

 must include an acquaintance with the mining and working of precious stones, their use in 

 jewellery and ornaments, and other subjects of a somewhat technical nature. 



Another important branch of the same subject is the determination of gems and the 

 recognition of the features which distinguish them from deceptive imitations in glass, or 

 from less valuable minerals of similar appearance. Long familiarity with the appearance of 

 different stones will, in many cases, enable a dealer or amateur, even though destitute of 

 mineralogical knowledge, to identify any given stone at a glance. In other cases, however, 

 a person who depends in this way upon his memory and sense of recognition, is very likely 

 to fall into error, which a scientific mineralogist would avoid by the use of exact methods of 

 determination. It is therefore greatly to the advantage of persons who buy and sell these 

 costly objects to make themselves acquainted with the principles and methods of mineralogy 

 here laid down. Not only does a sufficient practical knowledge of this subject help in 

 avoiding errors of determination, but it also enables one to gather from rough stones 

 valuable indications of the purposes to which they are most suited, and the methods of 

 working most advantageously employed. 



The first part of the present work will be devoted to a consideration of the mineral 

 characteristics which are of importance to the specialist in gems, a general consideration of 

 the mode of occuiTence of precious stones, and, finally, certain matters relating to the 

 application and working of these stones. The second part will contain a particular and 

 detailed account of every mineral which has been used for ornamental purposes, with special 

 reference to precious stones ; while the third part epitomises the characters to be relied on in 

 determining precious stones and for distinguishing them from other precious stones and 

 from imitations. 



