Gemstones & Pearls:News
Lore of the Rings
The curious multicolored rings sometimes seen when a gem is brought
in contact with an optically flat surface may provide the key to detecting
the age of fractures, say two gem experts
Necessity has given birth to an invention that may help detect whether
a fracture in a gemstone is old or new. Placing an optical flat on a flat
facet of a well-polished gemstone allows you to see "Newton rings,"
which are concentric rings appearing between the flat and the gem's surface.
(An optical flat is a piece of fused silica or quartz flattened and polished
to extremely high tolerance.)
Optical flats have not been used in gemology until now. The idea is the
brainchild of Ray Zajicek, owner of Equatorian Imports, Dallas, TX, and
Fred Ward of Gem Book Publishers and Blue Planet Gems, Bethesda, MD. The
two men hit upon the technique while trying to find a way to solve Ward's
thorny legal troubles with a 3.66-ct. emerald (Professional Jeweler,April
1998, p. 49).
The phenomenon of Newton rings may determine whether gemstones were damaged
before polishing, which then would indicate whether it occurred before or
after it was sold it to a customer. If you place an optical flat over a
facet that contains a fracture, Ward says, one of two things may happen:
- The spherical nature of the concentric Newton rings is broken at the
fracture point, indicating a dislocation in the surface of the gem. This
would suggest the gem was damaged after faceting, otherwise the faceting
process would have smoothed the surface.
- The spherical nature of the concentric rings stays intact, suggesting
the fracture occurred before it was faceted. This means that if the history
of a gemstone is documented well, especially its weight after cutting and
polishing, you could determine whether a fracture occurred at the gem's
point of origin (naturally) or after faceting.
If proven effective, this gemological tool could be used by jewelers who
take in gems and jewelry for repair, gemstone dealers who buy overseas and
insurance companies investigating claims.
Zajicek first noticed Newton rings on gems placed flat under a glass
at his display counter. Ward saw rings on gems in circular gem containers
with tight-fitting plastic lids. Both wondered whether there could be a
The two conducted months of experiments, documenting and photographing
dozens of gemstones to understand the nature of fractures induced,
natural and in repolished gemstones. Ward says he also hired fracture experts
to review his findings.
The experiments with the optical flats were undertaken as a way to help
bring an end to Ward's continuing legal struggle. He's trying to prove a
large fracture occurred in an emerald after he sold it and not before, as
the plaintiff alleged in a lawsuit she filed against him.
Ward says he did disclose two small fissures in the pavilion of the emerald
at the time of sale, but contends the large fracture occurred later when
the plaintiff knocked her ring at a kitchen counter. She says the fracture
was always there and was fracture-filled and not visible before it was sold.
A judge agreed with the plaintiff and ruled in her favor.
Based on the Newton ring evidence and other findings, however, Ward filed
a motion for a new trial in mid-August. A decision on a new trial was pending
at press time. With the studies Ward and Zajicek have conducted with optical
flats, they hope to prove the fracture occurred when the ring was knocked
and that it was fracture-filled some time after that. Ward's photographs
illustrate the use of the optical flat in fracture detection.
||This picture of a 3.66-ct. emerald shows a large fracture system across
the table. The emerald is at the center of litigation about whether the
fracture occurred naturally and was filled before it was sold or whether
it occurred when the new owner hit the stone on a counter and the fracture
was filled later.|
||The same emerald, under an optical flat, shows interrupted "Newton
rings," or rings that are not uniformly concentric in the area of the
fracture. This indicates a surface crack happened after the emerald was
faceted and sold, otherwise the surface would have been smoothed during
the faceting process.|
All photographs © Fred Ward, 1998
|A natural fissure on the pavilion of the same emerald was disclosed to the
consumer at the time of the sale. This picture, taken with an optical flat
over that fissure, shows uninterrupted concentric "Newton rings."
This suggests the fissure, which was present at the time of faceting, suffered
no changes, even though the emerald endured later trauma.|
What Is a Newton Ring?
are the concentric circles that appear when two flat transparent or semitransparent
surfaces are in close proximity.
Named for scientist Sir Isaac Newton (of law of gravity fame), Newton
rings are caused by light reflection and refraction. The rings can be seen
on the flat polished facets of gemstones when glass, an optical flat or
even a transparent gemstone case lid is held close. Seen here is an optical
flat in contact with a gemstone.
Newton rings also commonly appear when using a transparency on an overhead
projector, when printers and photographers scan film and on soap bubbles.
by Robert Weldon, G.G.
Copyright © 1998 by Bond Communications.