| In the business of buying and selling
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| | rubies and blue sapphires changes in the
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| precious stones there are a number of
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| | course of a day, and all specified what
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| little tricks picked up along the way,
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| | times those stones look best/worst. But,
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| tricks that often make the difference
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| | to the authors' astonishment, there was
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| between profit and loss. Collectively, we
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| | no consensus as to what those times are.
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| might call them "experience," for that is
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| | This was all the more interesting in that
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| normally how they are acquired and the
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| | a few stated that they try to coordinate
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| price is, usually, high. "Experience" of
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| | their buying/ selling of these stones
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| this sort is not found in gemological
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| | with the time of day in which the color
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| texts; it comes only through hard knocks
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| | appearance was best (= selling) or worst
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| - i.e., buying stones from someone who
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| | (= buying).
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| has a bigger box of experience than your
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| | Spurred on by curiosity, the authors and
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| own - or, via a bit of friendly advice
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| | two other AIGS staff carried out their
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| passed on by one who has been there
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| | own experiments. A selection of rubies
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| before. Most dealers have a collection of
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| | and blue sapphires of mixed "type
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| this "experience," kept in a box at the
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| | categories" (see Sersen, 1988) was
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| back of the safe or in some dusty drawer.
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| | periodically examined for two weeks.
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| It amounts to the small pile of gems
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| | North and east window lighting was used.
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| which are unsalable; the gems you have
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| | Weather conditions during this period
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| learned valuable lessons by buying. In
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| | ranged from bright and sunny to dark and
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| other words, gems you should not have
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| | rainy. The purpose of these experiments
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| bought in the first place.
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| | was, of course, to see if the stones
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| One bit of experience that every stone
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| | would change at all in color appearance.
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| dealer worth his rocks soon acquires is
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| that a stone's appearance is not
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| | The gems were viewed four times daily.
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| constant. Instead, it can and often does
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| | Hue, lightness and saturation was
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| change with the quality of light under
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| | recorded on each occasion, together with
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| which it is viewed. And a change in color
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| | respective weather conditions. These
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| appearance often means a change in value.
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| | notations were based strictly on visual
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| In the days before electric light
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| | observation. No conclusive results were
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| sources, traders could only view their
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| | had, possibly because no comparison
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| prospective purchases under natural light
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| | reference was used; only the testers'
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| or by the light of a candle. Natural
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| | memories were involved, just like with
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| light means direct sunlight and skylight
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| | most dealers.
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| (light coming from all directions of the
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| | Now more curious than ever, the authors
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| sky except directly from the sun).
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| | took a formal written survey of 20
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| Some dealers would examine a stone at
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| | colored-stone traders in order to compare
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| various times of the day, realizing that
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| | their answers and see what patterns, if
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| the position of the sun in the sky,
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| | any, might emerge.
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| together with weather conditions,
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| | The questions asked concerned the
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| affected overall color appearance; others
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| | lighting conditions used for buying and
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| took it one step further, viewing the gem
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| | selling, whether rubies/blue sapphires
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| in sunlight, skylight and in the shade of
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| | change color appearance at different
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| a tree in order to get an idea of how it
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| | times of the day (and if so, when do they
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| would look in any lighting situation.
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| | look best/worst) and specifically what
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| Similar practices continue to this day,
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| | factors are thought responsible for color
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| despite the availability of artificial
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| | appearance changes when such changes are
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| lights of various kinds.
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| | seen.
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| So, why examine gems under natural light,
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| | All 20 traders were interviewed in
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| the quality of which is subject to a
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| | Bangkok. They consisted of 9 Thais, 6
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| myriad of changing weather conditions,
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| | Americans, 3 Burmese, 1 Canadian and 1
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| when our Modern Age offers us
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| | Malaysian. The majority are local
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| incandescent and fluorescent (including
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| | wholesalers and sales personnel for local
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| simulated daylight) lighting? For that
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| | wholesalers. The others consist of
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| matter, why bother to view a gem under
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| | Thailand-based brokers and overseas-based
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| more than one light source, be it natural
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| | dealers who buy in Thailand and/or Sri
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| outdoor light at a given time(s) of the
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| | Lanka and sell in Europe and/or America.
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| day vs. the stone's appearance in the
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| | The trade experience of those questioned
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| shade, or in fluorescent simulated
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| | ranged from 2 to 50 years, with most
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| daylight vs. incandescent lighting? The
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| | having at least 10 years experience.
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| answers to those questions lie in whether
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| | Every attempt was made not to phrase
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| you are an astute buyer or seller, and in
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| | questions in a leading way. People were
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| what part of the world you happen to be
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| | simply asked questions and encouraged to
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| conducting business.
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| | "talk on" for as long as they wanted,
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| "One bit of experience that every stone
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| | without prejudicing comments from the
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| dealer worth his rocks soon acquires is
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| | interviewer.
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| that a stone's appearance is not
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| | "All agreed that the color appearance of
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| constant. Instead, it can and often does
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| | rubies and blue sapphires changes in the
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| change with the quality of light under
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| | course of a day, and all specified what
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| which it is viewed. And a change in color
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| | times those stones look best/worst. But,
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| appearance often means a change in
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| | to the authors' astonishment, there was
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| value."
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| | no consensus as to what those times are."
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| Viewing gems under natural light
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| | Survey results
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| As in other parts of the world, it is
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| | What lighting do you use when buying
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| common practice in Thailand for dealers
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| | stones?
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| and professional buyers to view colored
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| | Most people (75%) said they buy ruby and
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| stones at a table situated at a window.
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| | sapphire after examining those stones
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| Natural light is the accepted lighting
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| | under natural skylight only. Of those,
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| "standard," some dealers and buyers
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| | seven people prefer north or northwest
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| preferring north skylight only.
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| | skylight, seven use any direction of
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| In the days before the GIA Diamondlite,
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| | skylight, one specified north or south
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| such was also the case internationally
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| | skylight and one south skylight only. Of
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| with the color grading of diamonds.
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| | the remaining 20%, one buys only after
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| Writing in 1916, Frank B. Wade notes in
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| | viewing each stone under north skylight
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| his classic volume on diamonds:
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| | and direct sunlight; one uses north
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| "In the first place see that you have a
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| | skylight or a "daylight lamp"; two view
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| good north light, unobstructed by
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| | their prospective purchases under
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| buildings or other objects. There must
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| | multiple natural and artificial lighting
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| not be any coloured surface near by to
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| | conditions; one said he buys using
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| reflect tinted light, as a false estimate
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| | "whatever lighting arrangement happens to
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| might easily result."In the second place,
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| | be available."
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| do not attempt to judge stones at all
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| | Lighting used when selling stones?
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| closely except in the middle of the day,
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| | The majority (55%) of those questioned
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| say between 10 A.M. and 2 P.M. Very
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| | said they use skylight for selling as
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| erroneous results may easily be had by
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| | well as buying. Several stated
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| neglecting this precaution."Dark or dull
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| | categorically that the color appearance
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| days should be avoided also. One must
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| | of rubies and sapphires changes with the
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| have plenty of good neutral light to make
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| | time of day and they therefore prefer to
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| fine comparisons."
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| | buy in "bad light" and sell in "good
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| What Mr. Wade has to say about north
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| | light." The rational behind this is that
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| light and (especially) weather conditions
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| | if the stone appears reasonably nice
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| is echoed by many local colored-stone
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| | under less complimentary lighting, it
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| traders today. However, the authors of
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| | will look good under any (natural)
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| this article were particularly struck by
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| | lighting. Selling in "good light" means
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| the comment "between 10 A.M. and 2 P.M."
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| | exactly what it implies: during times
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| as it is reminiscent of remarks heard in
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| | when natural lighting conditions make the
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| Thailand and Burma about rubies and blue
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| | gem look best.
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| sapphires looking "better" or "worse" at
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| | One dealer said he buys in Sri Lanka
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| different times of day.
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| | using only northwest skylight, and sells
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| So, wondered the authors, does the
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| | in his U.S. office under quartz halogen
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| quality of natural light vary enough to
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| | lighting. Another stated she buys rubies
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| cause noticeable differences in the
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| | under north skylight, but prefers selling
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| appearance of rubies and blue sapphires
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| | them under "direct sunlight in the
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| at different times? Not only had Bangkok
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| | afternoon, because the light is yellow."
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| dealers mentioned this before, but some
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| | In both instances, the lighting used for
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| had gone so far as to say that they
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| | selling is perceived as complimentary to
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| regulate their buying and selling
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| | the gem's color appearance.
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| according to the time of day and weather
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| | The rest largely buy in skylight and sell
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| conditions.
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| | in whatever lighting is available or
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| It was decided to telephone a few local
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| | under lighting conditions expressly
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| colored-stone dealers, all of whom have
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| | requested by a customer, such as skylight
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| been in the trade for years, and ask them
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| | from a particular window direction.
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| the following questions:
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| | Obviously, dealers who do all their
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| Do rubies and/or blue sapphires change
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| | buying and selling from one office
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| appearance at different times of the
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| | location have more control over lighting
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| day?If yes, when do rubies look better
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| | conditions than does a broker who must
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| worse? When do blue sapphires look better
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| | sell - and accept consignments - under
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| worse?
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| | whatever lighting is available, natural
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| All agreed that the color appearance of
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| | or artificial.
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