Buying and selling gems

In the business of buying and selling preciousAll agreed that the color appearance of rubies and
stones there are a number of little tricks pickedblue sapphires changes in the course of a day,
up along the way, tricks that often make theand all specified what times those stones look
difference between profit and loss. Collectively,best/worst. But, to the authors' astonishment,
we might call them "experience," for that isthere was no consensus as to what those times
normally how they are acquired and the price is,are. This was all the more interesting in that a
usually, high. "Experience" of this sort is not foundfew stated that they try to coordinate their
in gemological texts; it comes only through hardbuying/ selling of these stones with the time of
knocks - i.e., buying stones from someone whoday in which the color appearance was best (=
has a bigger box of experience than your own -selling) or worst (= buying).
or, via a bit of friendly advice passed on by oneSpurred on by curiosity, the authors and two
who has been there before. Most dealers have aother AIGS staff carried out their own
collection of this "experience," kept in a box at theexperiments. A selection of rubies and blue
back of the safe or in some dusty drawer. Itsapphires of mixed "type categories" (see Sersen,
amounts to the small pile of gems which are1988) was periodically examined for two weeks.
unsalable; the gems you have learned valuableNorth and east window lighting was used. Weather
lessons by buying. In other words, gems youconditions during this period ranged from bright
should not have bought in the first place.and sunny to dark and rainy. The purpose of
One bit of experience that every stone dealerthese experiments was, of course, to see if the
worth his rocks soon acquires is that a stone'sstones would change at all in color appearance.
appearance is not constant. Instead, it can andThe gems were viewed four times daily. Hue,
often does change with the quality of light underlightness and saturation was recorded on each
which it is viewed. And a change in coloroccasion, together with respective weather
appearance often means a change in value.conditions. These notations were based strictly on
In the days before electric light sources, tradersvisual observation. No conclusive results were had,
could only view their prospective purchases underpossibly because no comparison reference was
natural light or by the light of a candle. Natural lightused; only the testers' memories were involved,
means direct sunlight and skylight (light comingjust like with most dealers.
from all directions of the sky except directly fromNow more curious than ever, the authors took a
the sun).formal written survey of 20 colored-stone traders
Some dealers would examine a stone at variousin order to compare their answers and see what
times of the day, realizing that the position of thepatterns, if any, might emerge.
sun in the sky, together with weather conditions,The questions asked concerned the lighting
affected overall color appearance; others took itconditions used for buying and selling, whether
one step further, viewing the gem in sunlight,rubies/blue sapphires change color appearance at
skylight and in the shade of a tree in order to getdifferent times of the day (and if so, when do
an idea of how it would look in any lightingthey look best/worst) and specifically what
situation. Similar practices continue to this day,factors are thought responsible for color
despite the availability of artificial lights of variousappearance changes when such changes are seen.
kinds.All 20 traders were interviewed in Bangkok. They
So, why examine gems under natural light, theconsisted of 9 Thais, 6 Americans, 3 Burmese, 1
quality of which is subject to a myriad of changingCanadian and 1 Malaysian. The majority are local
weather conditions, when our Modern Age offerswholesalers and sales personnel for local
us incandescent and fluorescent (includingwholesalers. The others consist of Thailand-based
simulated daylight) lighting? For that matter, whybrokers and overseas-based dealers who buy in
bother to view a gem under more than one lightThailand and/or Sri Lanka and sell in Europe and
source, be it natural outdoor light at a givenor America. The trade experience of those
time(s) of the day vs. the stone's appearance inquestioned ranged from 2 to 50 years, with most
the shade, or in fluorescent simulated daylight vs.having at least 10 years experience. Every
incandescent lighting? The answers to thoseattempt was made not to phrase questions in a
questions lie in whether you are an astute buyerleading way. People were simply asked questions
or seller, and in what part of the world youand encouraged to "talk on" for as long as they
happen to be conducting business.wanted, without prejudicing comments from the
"One bit of experience that every stone dealerinterviewer.
worth his rocks soon acquires is that a stone's"All agreed that the color appearance of rubies
appearance is not constant. Instead, it can andand blue sapphires changes in the course of a
often does change with the quality of light underday, and all specified what times those stones
which it is viewed. And a change in colorlook best/worst. But, to the authors'
appearance often means a change in value."astonishment, there was no consensus as to
Viewing gems under natural lightwhat those times are."
As in other parts of the world, it is commonSurvey results
practice in Thailand for dealers and professionalWhat lighting do you use when buying stones?
buyers to view colored stones at a table situatedMost people (75%) said they buy ruby and
at a window. Natural light is the accepted lightingsapphire after examining those stones under
"standard," some dealers and buyers preferringnatural skylight only. Of those, seven people
north skylight only.prefer north or northwest skylight, seven use any
In the days before the GIA Diamondlite, such wasdirection of skylight, one specified north or south
also the case internationally with the color gradingskylight and one south skylight only. Of the
of diamonds.remaining 20%, one buys only after viewing each
Writing in 1916, Frank B. Wade notes in his classicstone under north skylight and direct sunlight; one
volume on diamonds:uses north skylight or a "daylight lamp"; two view
"In the first place see that you have a good norththeir prospective purchases under multiple natural
light, unobstructed by buildings or other objects.and artificial lighting conditions; one said he buys
There must not be any coloured surface near byusing "whatever lighting arrangement happens to
to reflect tinted light, as a false estimate mightbe available."
easily result."In the second place, do not attemptLighting used when selling stones?
to judge stones at all closely except in the middleThe majority (55%) of those questioned said
of the day, say between 10 A.M. and 2 P.M. Verythey use skylight for selling as well as buying.
erroneous results may easily be had by neglectingSeveral stated categorically that the color
this precaution."Dark or dull days should beappearance of rubies and sapphires changes with
avoided also. One must have plenty of goodthe time of day and they therefore prefer to buy
neutral light to make fine comparisons."in "bad light" and sell in "good light." The rational
What Mr. Wade has to say about north light andbehind this is that if the stone appears reasonably
(especially) weather conditions is echoed by manynice under less complimentary lighting, it will look
local colored-stone traders today. However, thegood under any (natural) lighting. Selling in "good
authors of this article were particularly struck bylight" means exactly what it implies: during times
the comment "between 10 A.M. and 2 P.M." as it iswhen natural lighting conditions make the gem
reminiscent of remarks heard in Thailand andlook best.
Burma about rubies and blue sapphires lookingOne dealer said he buys in Sri Lanka using only
"better" or "worse" at different times of day.northwest skylight, and sells in his U.S. office under
So, wondered the authors, does the quality ofquartz halogen lighting. Another stated she buys
natural light vary enough to cause noticeablerubies under north skylight, but prefers selling
differences in the appearance of rubies and bluethem under "direct sunlight in the afternoon,
sapphires at different times? Not only hadbecause the light is yellow." In both instances, the
Bangkok dealers mentioned this before, but somelighting used for selling is perceived as
had gone so far as to say that they regulate theircomplimentary to the gem's color appearance.
buying and selling according to the time of dayThe rest largely buy in skylight and sell in
and weather conditions.whatever lighting is available or under lighting
It was decided to telephone a few localconditions expressly requested by a customer,
colored-stone dealers, all of whom have been insuch as skylight from a particular window
the trade for years, and ask them the followingdirection. Obviously, dealers who do all their buying
questions:and selling from one office location have more
Do rubies and/or blue sapphires changecontrol over lighting conditions than does a broker
appearance at different times of the day?If yes,who must sell - and accept consignments - under
when do rubies look better/worse? When do bluewhatever lighting is available, natural or artificial.
sapphires look better/worse?