Article from GIA:
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Is There a Difference Between Natural and Laboratory-Grown
Diamonds?
Is There a Difference Between Natural and Laboratory-Grown Diamonds?
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Two specimens of faceted crystalized carbon - both are crystal
clear and give off a kaleidoscope of spectral colors in direct light. They
appear to be identical. One, however, is a billion or more years old and the
other was recently grown in a laboratory.
Both are diamonds, of course. The first is a natural diamond
created by forces deep within the young Earth. The second is from a laboratory
and possesses essentially the same chemical, physical and optical properties as
its natural counterpart.
Diamond – the material, not the gem – is a mineral consisting of
“essentially pure carbon crystalized in the isometric cubic system,” according
to the U.S. Federal Trade Commission (FTC), which develops trading guides for
the gem and jewelry industry.
Although the FTC says diamonds are essentially pure carbon, the
vast majority of natural diamonds contain trace amounts of other substances, particularly
nitrogen, which gives them a yellow color or (rarely) boron, which imparts a
blue color. In addition, they usually contain inclusions, tiny bits of foreign
material that were trapped in the still-forming diamond millions of years ago.
Laboratory-grown diamonds (also sometimes referred to as
man-made or synthetic diamonds) entered the gem and jewelry market in
commercial quantities about five years ago. Although identical in appearance to
natural diamonds, they have very subtle differences that can only be detected
by trained gemologists and sophisticated equipment designed for that purpose.
WHERE DO DIAMONDS
COME FROM?
Natural Diamonds
Natural diamonds formed deep in the earth under extreme pressure
and high temperature as long as three billion years ago. Volcanic activity
brought them to the surface where they lay in a type of volcanic rock formation
known as kimberlite pipes, waiting to be mined. Only about five percent of
kimberlite pipes contain enough diamond to make them economically feasible to
mine.
Laboratory-Grown Diamonds
Man-made diamonds suitable for industrial use were first
produced in a laboratory in the 1950s. While gem-quality diamonds were produced
in a laboratory for the first time in 1971, it was not until the mid-2010s that
colorless laboratory-grown diamonds entered the gem and jewelry market in
commercial quantities.
Today, laboratory-grown diamonds are created by two methods,
according to Dr. James Shigley, GIA Distinguished Research Fellow, who has been
researching laboratory-grown diamonds at GIA for more than 30 years.
High pressure, high temperature (HPHT) diamonds are produced in
a laboratory by mimicking the high pressure, high temperature conditions that
form natural diamonds in the Earth. This process produces a distinctively
shaped laboratory-grown diamond crystal.
The chemical vapor deposition (CVD) method involves breaking
down the molecules of a carbon-rich gas, such as methane, into carbon and
hydrogen atoms, which then are deposited on diamond seeds to produce a
square-shaped, tabular diamond crystal.
Growing diamonds by either method typically requires less than a
month for most sizes. Most CVD-grown diamonds require additional treatments
like heat or irradiation to enhance or change their colors after the growth
process.
Typically, laboratory-grown diamonds have weighed a carat or
less, but as technology and techniques improve, larger stones have appeared in
the market.
HOW CAN NATURAL
AND LABORATORY-GROWN DIAMONDS BE DISTINGUISHED FROM ONE ANOTHER?
It is essential that laboratory-grown diamonds can be identified
because consumers need to know what they are buying, and because there are
often significant price differences between them and natural gemstones.
As part of its mission to protect and inform the gem-buying
public, GIA offers diploma programs, including the GIA
Graduate Gemologist credential, and seminars that teach diamond
grading techniques and the latest methods used to distinguish natural from
laboratory-grown diamonds and diamond simulants.
Because laboratory-grown diamonds are essentially chemically and
optically the same as their natural counterparts, traditional gemological
observations and old-style “diamond detectors” are not able to tell them apart.
Identification at a professional gemological laboratory or using sophisticated
devices developed by GIA and other organizations are the only reliable methods
to separate them from natural diamonds.
Diamond Morphology – the
Telltale Factor
“Natural diamonds that formed in the Earth over millions of
years grow differently from diamonds created in a laboratory in a few weeks. In
addition, HPHT- and CVD-created diamonds have different growth morphology, or
how growth conditions influenced the shape of the diamond crystal,” said Dr.
Shigley.
GIA Senior Research Scientist Dr. Sally Eaton-Magaña further
explained, “The identification criteria for HPHT and CVD diamonds are quite
distinct from each other,” adding that laboratory-grown diamonds have become
much more varied over the last 10 to 15 years, requiring GIA researchers to
keep pace with new developments.
“We also regularly conduct research on emerging products and GIA
has a program to grow diamonds in the laboratory to stay ahead of any new
trends,” Dr. Eaton-Magaña said.
DOES GIA OFFER
GRADING FOR LABORATORY-GROWN DIAMONDS?
GIA tests every diamond submitted to its gemstone grading and
identification laboratory locations around the world to determine whether they
are natural or laboratory-grown.
GIA has issued reports for laboratory-grown diamonds for more
than 10 years. In March 2019, following the guidelines from the FTC, the
Institute announced it will change the name of the reports to GIA
Laboratory-Grown Diamond Reports starting in July 2019. To reduce the potential
for confusion, GIA grading reports for laboratory-grown diamonds look
significantly different from those for natural diamonds. In addition, the terms
used to report color and clarity grades for laboratory-grown diamonds are
different from those used for natural diamonds. Instead of D-to-Z color grades,
broader category terms (Colorless, Near-Colorless, Faint, Very Light and Light)
are used. Clarity grades, which are abbreviated on natural diamond reports
(VVS1, SI2, etc.), use broader descriptive category terms (i.e., Very Very
Slightly Included, Slightly Included) on the reports for laboratory-grown
diamonds.
WHAT ABOUT
DIAMONDS THAT ARE NOT SUBMITTED TO GEM LABS FOR GRADING?
To identify laboratory-grown diamonds, GIA developed the GIA iD100® screening
device. This desktop-sized instrument combines advanced spectroscopic
technology with GIA’s 60 years of diamond and gemstone identification research
to distinguish natural diamonds from laboratory-grown (HPHT and CVD) diamonds
and diamond simulants.
GIA also offers the GIA Melee Analysis Service,
which quickly and accurately screens parcels of very small diamonds – the most
prevalent in the market.
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