Passport to Obscurity
Obscurity is a lonely place,
right next door to oblivion.
While a passport typically conjures up images of freedom, the open road and travel to exotic locales, not every destination is five-star. This point was driven home during the examination of a group of yellow sapphires recently sent to the laboratory for identification.
The lot consisted of several yellow sapphires of
graduated weight, each with similar shape, facet arrangement and face-up color.
It appeared likely that all were intended for a single piece of jewelry.
gems of this type, inclusions
are often sufficient to immediately
identify the host as a natural
sapphire, as well as prove or
disprove heat treatment. When
present, a 3160 infrared peak
is also important evidence of
natural, untreated origin in
yellow sapphires. With but one
exception, all the sapphires
in the group contained obvious
visual micro-evidence of natural
origin, along with moderate
to strong 3160 peaks in the
infrared, both tickets to paradise.
sapphire, however, showed
no obvious inclusions and
no telltale 3160 peak, immediately
raising an alarm. This meant
it would require additional
examination consisting of
a detailed microscopic inspection
using a combination of fiber-optic
and darkfield illumination,
with polarized light, if
needed. Careful scrutiny
would be necessary if a decision
was to be reached as to the
search parties were sent out throughout
the stone on a facet-to-facet search.
All reported back empty-handed.
Except one. As the stone was rocked
to-and-fro, a weak flash of light
winked from the abyss. Zooming
in revealed a miniscule, inconspicuous
heat-damaged inclusion with
an associated mirror-reflective
discoid decrepitation halo (Figure 1).
While at just 0.01 mm
in diameter (as measured with an
eyepiece micrometer), this inclusion
was certainly tiny, it was all
that was needed to both eliminate
the possibility of synthetic origin
and prove heat treatment.
Figure 1. Destination unknown…
Although relatively small and inconspicuous at roughly 0.01 mm. diameter,
this heat-treatment damaged crystal with its diagnostic discoid
decrepitation halo (also produced by heat treatment) is all the proof needed to destroy the natural reputation of
its host yellow sapphire. Photomicrograph © John I. Koivula/microWorld
identification reports were
requested for every stone
and all except one received
natural, unheated reports.
While we do not
know the fate of this individual
gem, we suspect that
when the client studied the
reports, the guilty stone
was pulled and a natural
replacement found. The treated
stone is probably now destined
for a lesser piece of jewelry,
or perhaps it will simply
be placed somewhere in a
drawer, cast aside and forgotten.
Inclusions are passports, identification papers. From the transparent calcite rhombs in Burma rubies to the rutile arrows in Sri Lankan sapphires, these tiny disturbances so often provide entreé to a better place. But as this tale tells, inclusions may also be tickets to a less-than distinguished future.
inclusions provide proof
of natural origin, they allow
entry to paradise. But when
the reverse is true, when
they prove a gem to be treated
or synthetic, they can be
passports to obscurity. And
obscurity is but a short
walk from the
abyss of oblivion.
John I. Koivula is one of the world's most famous gemologists and photomicrographers. Author of several books and more than a thousand articles, he was also the scientific advisor to the famous MacGyver television series.
Richard Hughes (left) is
the author of the classic Ruby & Sapphire and over 100 articles on various aspects of gemology. Many of his writings can be found at www.ruby-sapphire.com.
First published in November 2005, while John and I were at the AGTA GTC. Working with John was one of the greatest pleasures of my life, sadly far too brief. Looking back, I can only wonder what might have been… Thanks to Donald Allen for suggesting the above
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Posted 14 October, 2011; last updated
7 March, 2013