Knowing the Difference

Natural diamonds have long fascinated mankind with their unique physical and visual properties. Features such as exceptional hardness,
durability, light reflectivity (brilliance) and dispersion (fire)distinguish them from other gems. The beauty and universal appeal of natural
diamonds come at a price, as the recovery and fashioning of such rare gems are challenging. For decades, researchers have sought alternatives
by creating less expensive “look-a-likes” in the form of simulants and, more recently, “duplicates” with synthetic diamonds. Though such attempts
by man to recreate the properties and structure of natural diamonds are nothing new, a rapid increase in synthetic diamond growth technology
over the past decade has ledto real concerns regarding their identification.

Fortunately, GIA has followed the developments of synthetic diamonds for more than 60 years. This continuum—combined with fundamental research on tens of millions of natural diamonds—allows GIA to accurately identify synthetic diamonds. In order to protect yourself and your clients against misrepresentations and misconceptions surrounding natural diamonds, synthetic diamonds, and diamond simulants, it is important that you understand the differences among them and the means of their identification. Unlike diamond simulants, which can be recognized by using standard gem testing, synthetic diamonds have essentially the same chemical composition and crystal structure as natural diamonds, but are made in laboratories—not grown in the earth. Because their optical and physical properties are nearly identical to natural diamonds’, identifying synthetic diamonds is complex. However, because of their artificial growth environments, synthetic diamonds exhibit several diagnostic features that allow for their detection in gemological laboratories.

Synthetic Diamond Identification

Because of the contrasting conditions of naturaland artificial formation, synthetic diamondsdisplay several features which allow
them to begemologically distinguished from natural diamonds.These include visual characteristics such as colorzoning, dark metallic
inclusions, weak strainpatterns and distinctive patterns and colors ofultraviolet fluorescence. Because they representtypes of diamonds
that are rare in nature, syntheticdiamonds also possess additional features thatcan be detected with gemological instruments.

Decades of research, in addition to the use anddevelopment of advanced scientific instrumentation,enable GIA to accurately identify syntheticdiamonds. GIA’s Diamond Check™ and recentintroduction of a fully automated Melee AnalysisService allow for fast and accurate separationof loose natural diamonds from loose syntheticsand simulants. The challenge to develop a similarmethod for analysis of mounted stones is morecomplex due to coverage from metal settings.Information on synthetic diamond identificationhas been published extensively in GIA’s peerreviewedGems & Gemology over the last 30 years.

Natural Diamonds

Natural diamonds are a wonder of science,as they occur only when atoms of carbon areexposed to high pressures and temperaturesabout
100 miles (160 kilometers) below the earth’ssurface in what geologists call the upper mantle.Diamond crystals reside in these extreme
mantleconditions for millions of years. The crystalsthat grow under these conditions have a uniquestructure we associate with natural diamonds.

Natural diamond crystals sometimes incorporate solidsmall inclusions of diamonds or other minerals intotheir structure as they grow. While mineral inclusionsare often considered a negative clarity feature in apolished diamond, they are of tremendous value togeoscientists. Natural diamonds provide a way forthese mineral inclusions to be preserved and broughtto the earth’s surface where they can be scientificallystudied. Because certain inclusions contain radioactiveelements that decay at a known rate, the minerals canalso be used to calculate the age of diamond formation.

Following their extended time in residence in themantle, some diamonds are brought to the earth’ssurface by volcanic eruptions of kimberlite magma.Geologists believe that the diamonds are transportedby the magma very quickly over the 100-mile distance(in just a week or more), so that the diamonds are notphysically changed in the process and transformed tographite. During this rapid upward journey, the diamondcrystal can, however, break along cleavage directions,and undergo other

Synthetic Diamonds

Although their use for jewelry purposes is a somewhatrecent occurrence, synthetic diamonds have beenproduced for industrial applications
since the 1950s.Unlike natural diamonds, synthetic diamonds aregrown in laboratories, over a very short period oftime – likely just two
or three weeks (or less). Alonger growth period results in larger crystals;however, steady environmental conditions must bemaintained to
ensure the formation of high-qualitycrystals. Currently, the production of syntheticdiamonds in melee sizes is what is most encountered.The
drastically shorter growth period of syntheticdiamonds results in features that are of diagnostic

Two artificial growth methods are used to createsynthetic diamonds: HPHT and CVD. HPHT (highpressure/high temperature) synthesis, developed inthe 1950s, uses high temperatures and pressures, amolten metal flux and a diamond seed to initiate crystalformation. The result is a distinctive crystal shape whichis a combination of octahedral and cube faces and aflat base. The HPHT process more closely mirrors theconditions of natural diamond formation than CVD.The CVD (chemical vapor deposition) method, whichwas mostly developed during the past decade, producesdiamonds through the use of lowpressures and high temperaturesin a vacuum chamber. A carboncontaininggas such as methane isintroduced into the chamber, and gasmolecules break down there into theconstituent atoms. The carbon atoms“rain” down onto flat diamond seedplates, resulting in a square-shaped,tabular synthetic diamond crystal.

Diamond Simulants

Various materials have been used as imitations orsubstitutes for diamonds since ancient times. Thesematerials, often referred to as diamond simulants,may grow naturally in the earth or artificially ina lab. Years ago, the colorless varieties of somecolored stones (i.e., quartz) were used to simulatediamond. Today, the most common simulants arecubic zirconia (zirconium oxide, or CZ), and to alesser extent, synthetic moissanite (silicon carbide).Because simulants differ completely from diamond,they display diagnostic properties by which theycan be recognized with standard gem testingtechniques, observations under magnificationand commercially available “diamond testers.”

Laboratory-Grown Diamonds and the GIA Laboratory-Grown Diamond Reports

Laboratory-Grown Diamonds

HPHT Diamonds

HPHT laboratory-grown
diamonds are grown in
laboratories at high pressures
and high temperatures.
A diamond seed is used and
growth from a flux material
(molten metal alloy) takes place
over a period of several weeks.

CVD Diamonds

CVD diamonds are grown at
high temperatures and very
low pressures in a vacuum
chamber. Tabular laboratorygrown
diamond crystals up
to several carats are formed
on flat diamond seed plates
during growth periods of one
week or more.

Natural Diamonds

Natural Diamonds

Natural diamonds occur only
when the right combination
of atomic elements meets
at high pressures and
temperatures about 100 miles
below the earth’s surface.
The crystal that grows under
these conditions has a unique
structure we associate with
natural diamonds.

Laboratory-Grown Diamonds

Unlike natural diamonds, laboratory-grown diamonds are grown over a very short period of time — typically two to three weeks or less. A longer growth period results in larger crystals, however, steady heat and pressure must be maintained to ensure the formation of highquality gem crystals. While laboratory-grown diamonds in melee sizes are most often encountered in the industry, larger stones are available and their marketing can benefit from an association with a GIA Laboratory-Grown Diamond Report.

Two crystal growth methods are used to create laboratory-grown diamonds: HPHT and CVD. HPHT (high pressure, high temperature) synthesis, developed in the 1950s, uses high temperatures and pressures from a molten metal and a diamond seed to initiate crystal formation. The HPHT process more closely mirrors the conditions of natural diamond formation than CVD. The chemical vapor deposition (CVD) method produces diamonds through the use of low pressures and high temperatures in a vacuum chamber. While originally developed in the 1950s, progress on the technology for single crystal growth has been rapid during the past decade.

GIA Laboratory-Grown Diamond Report

GIA offers a Laboratory-Grown Diamond Report that includes the same information as the GIA Diamond Report for natural D-to-Z diamonds. The information presented in the report is important in the marketing of laboratory-grown diamonds and, being from GIA, a respected, independent third-party, can add value. Like the GIA Diamond Grading Report for natural diamonds, the GIA Laboratory-Grown Diamond Report includes the critical information related to the diamond’s cut such as polish, symmetry and, for round brilliants, a GIA cut grade. These are all factors used to understand the interplay of light patterns that affect the perceived sparkle and beauty of the diamond. Weight and measurements, as well as a GIA plotting diagram, accurately capture characteristics of the stone to aid in its re-identification. GIA laboratory-grown diamond reports include 4Cs color and clarity specifications for laboratorygrown diamonds on the same scales as GIA’s grading reports for natural diamonds. The specifications do not correlate to nature’s continuum of rarity. The digital-only reports for laboratory-grown diamonds have a distinct format to fully different from reports for natural diamonds. The laboratory-grown diamond’s girdle is laser inscribed with “Laboratory-Grown” and the GIA report number.


Identifying laboratory-grown diamonds is complex because their optical and physical properties are nearly identical to those of natural diamonds. However, because of their artificial growth environments, laboratory-grown diamonds exhibit several diagnostic features that allow GIA to readily identify them.

GIA’s Commitment to Industry Assurance

Decades of research enable GIA to accurately identifylaboratory-grown diamonds. Advancements inlaboratory-grown diamond growth technology willcontinue to present challenges. GIA operates to ensurethe public trust in gems and jewelry and will continueto make significant investments into research tounderstand the coming challenges and improveand expand upon its identification capabilities.Whether a diamond is natural or laboratory-grown, itis important that it is accurately represented and theinformation surrounding it is not false, inaccurateor misleading. GIA’s Laboratory-Grown DiamondReports can provide this assurance to consumers andthe trade.