xiv Preface.
The
chapter devoted to the various methods and tests for ascertaining the
class to which any special gem belongs will, the writer conceives, be
of considerable assistance even to persons accustomed to the trade,
many of whom from long habit and experience may be judges of the value,
but are yet wholly unacquainted with the practical tests required. As
stated in the body of the work, the tourmaline is sometimes mistaken
for the ruby, the pink topaz for the Balas ruby, and occasionally the
white sapphire and topaz pass for the diamond, even with those who
profess to be acquainted with gems. The tables of hardness, specific
gravity, and electrical properties, however, will prevent any one from
falling into these errors, as nothing can be more easy than, from the
data given, to ascertain to which class any particular stone belongs.
At first it was the author's intention to publish simply a Bibliographical Account of Books relating to Precious Stones,—a
list of the various works and treatises that he has met with from time
to time,—which would have formed a pamphlet guide for the student or
collector; but his final determination to gather up in a small volume
the distinguishing characteristics of each gem, with such advice
respecting their identification and treatment as was known to be
thoroughly reliable and of practical use, also led him to place the
bibliographical memoranda as an Appendix to the rest of the work.
