ing
a backward glance over his experience recalls the many serious mistakes
that have come to his knowledge. Many more have doubtless occurred
without detection. Several times recently the author has come across
cases where large dealers have been mistaken in their determination of
colored stones, particularly emeralds. Only the other day a ring was
brought to me that had been bought for a genuine emerald ring after the
buyer had taken it to one of the dealers in his city and had paid for an
examination of it, which had resulted in its being declared genuine. On
examining the stone with a lens of only moderate power, several round
air bubbles were noted in it, and on barely touching it with a file it
was easily scratched. The material was green glass. Now, what was said
about the dealer who sold it and the one who appraised it may be
imagined. The long chain of adverse influence which will be put in
action against those dealers, even though the one who sold the stone
makes good the loss, is something that can be ill afforded by any
dealer, and all this might have been avoided by even a rudimentary
knowledge of the means of distinguishing precious stones. The dealer was
doubtless honest, but, through carelessness or ignorance, was himself
deceived.

Our first few lessons will therefore be concerned chiefly with learning
the best means of telling the different stones from one another.

CONTENTS

PAGE
PREFACE iii

LESSON
I.--HOW STONES ARE DISTINGUISHED FROM ONE ANOTHER 1

II.--REFRACTION 4

III.--DOUBLE REFRACTION 8

IV.--ABSORPTION AND DICHROISM 15

V.--SPECIFIC GRAVITY 23

VI.--SPECIFIC GRAVITY DETERMINATIONS 31

VII.--LUSTER AND OTHER REFLECTION EFFECTS 38

VIII.--HARDNESS 47

IX.--HARDNESS (_Continued_) 55

X.--DISPERSION 60

XI.--COLOR 66

XII.--COLOR (_Continued_) 75

XIII.--COLOR (_Continued_)