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Precious Stones

104 Page Ebook

BECAUSE of the rapid increase in knowledge about precious stones on the part of the buying public, it has become necessary for the gem merchant and his clerks and salesmen to know at least as much about the subject of gemology as their better informed customers are likely to know.
In many recent articles in trade papers, attention has been called to this need, and to the provision which Columbia University has made for a course in the study of gems. The action of the National Association of Goldsmiths of Great Britain in providing annual examinations in gemology, and in granting certificates and diplomas to those who successfully pass the examinations, has also been reported, and it has been suggested that some such[vi] course should be pursued by jewelers' associations in this country. The greatest difficulty in the way of such formal study among our jewelers and gem merchants is the lack of time for attendance on formal courses, which must necessarily be given at definite times and in definite places.
As a diamond salesman was heard to say recently: "The boss said he wanted me to take in that course at Columbia, but he didn't tell me how I was going to do it. Here I am a thousand miles from Columbia, and it was only six weeks ago that he was telling me I ought to take that course. I can't stay around New York all the time." Similarly those whose work keeps them in New York might object that their hours of employment prevented attendance on day courses, and that distance from the university and fatigue prevent attendance on night courses. The great mass of gem dealers in other cities must also be considered.[vii]
It will therefore be the endeavor of this book to provide guidance for those who really want to make themselves more efficient in the gem business, but who have felt that they needed something in the way of suggestion regarding what to attempt, and how to go about it.
Study of the sort that will be suggested can be pursued in spare moments, on street cars or elevated trains, in waiting rooms, or in one's room at night. It will astonish many to find how much can be accomplished by consistently utilizing spare moments. Booker T. Washington is said to have written in such spare time practically all that he has published.
For the practical study of the gems themselves, which is an absolutely essential part of the work, those actually engaged in the trade have better opportunities than any school could give and, except during rush seasons, there is plenty of time during business hours for such study. No intelligent employer will begrudge such use of time for which he is paying, if the[viii] thing be done in reason and with a serious view to improvement. The frequent application of what is acquired, as opportunity offers, in connection with ordinary salesmanship, will help fix the subject and at the same time increase sales.
Many gem dealers have been deterred from beginning a study of gems because of the seeming difficulties in connection with the scientific determination of the different varieties of stones. Now science is nothing but boiled-down common sense, and a bold front will soon convince one that most of the difficulties are more apparent than real. Such minor difficulties as exist will be approached in such a manner that a little effort will overcome them. For those who are willing to do more work, this book will suggest definite portions of particular books, which are easily
available, for reference reading and study—but the lessons themselves will attempt to teach the essential things in as simple a manner as is possible.[ix]
Perhaps the first essential for the gem merchant is to be able surely to distinguish the various stones from one another and from synthetic and imitation stones.
That such ability is much needed will be clear to anyone who in casting 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.[x] 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

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)
87
XIV.—
COLOR (Concluded)
93
[xii]XV.—
HOW TO TELL SCIENTIFIC STONES FROM NATURAL GEMS
99
XVI.—
HOW TO TEST AN
109
"UNKNOWN" GEM
XVII.—
SUITABILITY OF STONES FOR VARIOUS TYPES OF JEWELS, AS DETERMINED BY HARDNESS, BRITTLENESS, AND CLEAVABILITY
119
XVIII.—
MINERAL SPECIES TO WHICH THE VARIOUS GEMS BELONG AND THE CHEMICAL COMPOSITION THEREOF
133
XIX.—
THE NAMING OF PRECIOUS STONES
149
XX.—
THE NAMING OF PRECIOUS STONES (Concluded)
164
XXI.—
WHERE PRECIOUS STONES ARE FOUND
179
XXII.—
HOW ROUGH PRECIOUS STONES ARE CUT
201
XXIII.—
HOW ROUGH PRECIOUS STONES ARE CUT AND WHAT CONSTITUTES GOOD "MAKE" (Concluded)
213
[xiii]XXIV.—
FORMS GIVEN TO PRECIOUS STONES
227
XXV.—
IMITATIONS OF PRECIOUS STONES
237
XXVI.—
ALTERATION OF THE COLOR OF PRECIOUS STONES
250
XXVII.—
PEARLS
258
XXVIII.—
CULTURED PEARLS AND IMITATIONS OF PEARLS
277
XXIX.—
THE USE OF BALANCES AND THE UNIT OF WEIGHT IN USE FOR PRECIOUS STONES
283
XXX.—
TARIFF LAWS ON PRECIOUS AND IMITATION STONES
294
BIBLIOGRAPHY
301
INDEX
313

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