When you hold a sparkling stone up to the light, how do you know if it is a genuine diamond or a convincing lookalike? Understanding how lab-grown diamonds are made gives you context for why some stones test differently, and it helps you spot differences between natural diamonds, moissanite, and cubic zirconia using simple checks like a loupe inspection, thermal conductivity tester, fog test, UV fluorescence, and certificate verification.
This guide lays out easy, reliable methods—checking weight, clarity, refractive behavior, and grading reports—so you can confidently identify and verify genuine diamonds without guesswork.
To make those checks easier, PriceScope, the largest diamond and jewelry forum, lets you tap into honest conversations, clear how-to guides, and expert feedback so you can compare findings, ask questions, and build confidence fast.
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Natural diamonds form under extreme heat and pressure deep in the Earth. Their crystal lattice gives them a very high refractive index and strong dispersion. That combination produces bright white flashes, known as brilliance, and colorful flashes, known as fire. Look through a 10x loupe for sharp facet junctions and crisp facet edges; real diamonds typically exhibit sharp edges and well-defined facets, rather than the rounded facet edges commonly found in many simulants.
Cubic zirconia, moissanite, and white sapphire are common simulants of diamonds. Cubic zirconia shows more rainbow flashes and often looks too perfect. Moissanite has even stronger fire and can pass simple thermal tests because it conducts heat similarly to diamond. White sapphire has a lower refractive index and less sparkle than its counterparts. Under magnification, simulants often reveal different inclusions, rounded facets, or polishing marks that differ from natural or lab-grown diamonds.
Lab-grown diamonds have the same chemical composition and crystal structure as mined diamonds. They match in terms of hardness, refractive index, and thermal conductivity. The main differences come from growth patterns and trace elements. Labs can detect growth features and metallic inclusions that indicate specific production methods, and many lab-grown stones carry laser inscriptions on the girdle and lab reports from GIA, IGI, or other reputable laboratories.
High-pressure, high-temperature (HPHT) conditions recreate the conditions of the deep Earth. A carbon source sits on a diamond seed, and heat and pressure convert carbon into diamond. Metal catalysts used in this process can leave tiny metallic inclusions that gem labs can spot. Chemical vapor deposition, or CVD, is a process that grows diamond in a vacuum chamber. A methane-hydrogen gas mix breaks down in a plasma, and carbon atoms deposit on a seed plate, layer by layer. CVD often leaves growth banding that can be detected under specialized instruments and may be removed or altered through post-growth treatment.
Check the lab name, report number, and whether the report states natural or lab-grown. Examine the plot for inclusions, clarity grade, and cut grade. Confirm the carat weight and any notes about treatments. The report often tells whether the stone has laser inscriptions on the girdle that match the report number.
Thermal probe devices are handy but not definitive, because moissanite can mimic diamonds on thermal tests. Visual checks or a quick home test cannot detect a lab-grown origin. When in doubt, send the stone to a gem lab for grading and origin determination. Professional testing uses instruments that detect trace elements and growth features invisible to handheld tools.
Do you have an independent lab report, and can you share the report number? Is the diamond laser inscribed with that report number? Has the stone had treatments or color enhancements? Can I see detailed photos or videos under magnification? Request a return policy and an appraisal from a recognized laboratory if you plan to insure the stone.
Join thousands of engaged buyers, enthusiasts, and industry experts at PriceScope, the largest diamond and jewelry forum, who rely on our unbiased forums, advanced tools like the Holloway Cut Advisor, and carefully vetted vendor partnerships with trusted retailers like Whiteflash, James Allen, and Blue Nile. Start your diamond education journey today with our comprehensive guides, pricing insights, and sales pressure-free community support – because when it comes to diamonds, knowledge is your most valuable investment.
Real diamonds display distinctive brilliance due to their exceptional ability to bend and reflect light. When light enters a genuine diamond, it scatters bright white reflections known as brilliance. Unlike imitations such as cubic zirconia or glass, which often appear overly rainbow-colored or dull, real diamonds produce sharp, vivid flashes of white light. This unique light performance is a hallmark trait, visible even to the naked eye under good lighting conditions.
The quality of the diamond’s cuts also offers important clues. Genuine diamonds have sharply defined facets with crisp, precise edges formed through expert cutting techniques. These clean, angular edges contrast with the rounded or fuzzy facets typically found on fake stones. Additionally, natural diamonds may contain minute internal inclusions or tiny imperfections, confirming their natural origin, while a flawless appearance can sometimes suggest synthetic or imitation gems.
For diamond rings or other pieces, the craftsmanship of the setting is often indicative of the stone’s authenticity. Real diamonds are almost always mounted in high-quality precious metals such as gold or platinum. Look for hallmark stamps like 14K, 18K, 585, 750, 900, or 950, or PT on the metal, which signify genuine precious materials. Well-made settings will have secure, tight prongs or bezels holding the diamond firmly. Poorly made or flimsy settings often indicate that the diamond may be a fake.
When examining diamond earrings, compare both stones side by side under bright light. Authentic diamonds typically show consistent brilliance across the pair, reflecting bright white flashes and subtle rainbow hues equally. If one stone looks dull or its sparkle differs significantly, it suggests the earrings may not contain real diamonds. Also, inspect earring backs and posts for quality metals with proper markings, as genuine diamond earrings are usually paired with sturdy, weighted hardware.
Diamond bracelets, especially tennis bracelets, should exhibit uniform sparkle and quality across all stones. Each diamond ought to match closely in size, cut, and light performance when the bracelet is moved under light. The bracelet’s links and clasps should also feel solid and well-crafted, providing a secure hold for every diamond. Sloppy construction or uneven stone quality often signals imitation stones.
For necklaces featuring diamonds, focus not only on the main stone but also on the smaller accent diamonds, which should all shine with consistent brilliance. The metal chain should feel heavy enough to support the diamonds comfortably, and the clasp mechanism must be sturdy and well-made, with hallmarks indicating the presence of precious metals. High-quality clasps usually accompany authentic diamond necklaces, while weak or decorative clasps may be a warning sign.
Shine a bright flashlight straight onto the stone and watch the reflections. Real diamonds return intense white flashes, known as brilliance, and small, rainbow-colored flashes, called fire, due to their high refractive index and strong dispersion. Fake simulants often look duller or give weak reflections. Watch for an extreme white sparkle mixed with small, rainbow-colored flashes when you tilt the stone.
Hold the stone near a mirror and tilt it while watching reflections—diamonds scatter light strongly from many facets, producing lively reflections that jump as you move the gem. Many glass or cubic zirconia simulants show flat or muted reflections. Use a 10x loupe while doing this to inspect facet edges and a sharp girdle line, as a real cut diamond will show crisp facet junctions.
Drop a loose stone into a clear glass of water and see if it sinks quickly to the bottom. Diamonds are dense and will sink fast. If it stays suspended or floats, it is almost certainly not a diamond. Bear in mind that some simulants also sink, so use this as a quick clue, not as proof.
Breathe gently onto the stone to fog it and time how fast the fog clears. Diamonds conduct heat rapidly, so the fog should clear almost instantly, usually within a second. If the mist hangs for several seconds, the stone is likely to have poorer thermal conductivity. This method is best suited for loose rocks, as settings can trap heat and skew the results.
Shine a UV light on the stone in a dark room to check fluorescence. Many natural diamonds fluoresce blue under long-wave UV light, but the intensity varies from none to strong. A lack of fluorescence does not necessarily mean the stone is fake. Fluorescence provides a clue but cannot confirm authenticity alone; therefore, it should be paired with other tests.
Examine the gem in bright daylight or direct sunlight and look for sharp white brilliance plus small flashes of rainbow color. Cut quality affects how a diamond performs in natural light, so that a well-cut stone will show more life. Clean the stone before testing; oil and dirt can mute its sparkle and make a real diamond appear weak.
Check the mounting and look for metal hallmarks, like 14K, 18K, or PLAT. Jewelers typically set real diamonds in precious metals. If the setting is cheap or unmarked, you should be suspicious. Also, inspect the prongs and mounting style with a loupe to determine whether the setting appears mass-produced or designed to hold a valuable stone.
Draw a small black dot on white paper and place the loose stone flat on the paper. Look down through the stone from the top. A real diamond scatters light so strongly that the dot will blur or disappear. If you can read the dot sharply, you have a simulant. This works best on well-cut loose diamonds and less well on included or heavily clouded stones.
Set the stone flat side down on the printed text and try to read the letters through it. Diamonds bend and scatter light so much that text should be unreadable or highly distorted. If letters remain clear, you likely have a non-diamond material. Use clean, flat glass to stabilize the stone for a fair check.
Carry a 10 times loupe to inspect facet junctions and inclusions, a basic thermal conductivity diamond tester to check heat transfer, and a moissanite tester that detects double refraction. Electronic conductivity testers can yield false positives for moissanite, so it is recommended to compare test results. For absolute certainty, ask for a GI, an IGI, or AGS certificate, or have a trusted independent lab verify the stone.
Jewelers start with a 10x loupe and steady hands. They scan facets, facet junctions, the girdle, table, crown, and pavilion for crisp facet edges and polish lines. Natural diamonds commonly show tiny inclusions, feather lines, or pinpoint crystals. Look for metallic flux or curved growth lines instead; these often indicate lab-grown or simulant material. The way light returns from facets reveals a great deal about brilliance and scintillation. A loupe will not prove origin, but it does show clarity, polish, and cut quality that initiates the identification process.
Professionals measure carat weight using calibrated digital scales and compare it to the expected mass for the stone’s measured dimensions. The specific gravity of diamond is approximately 3.52. Cubic zirconia and glass are denser and will weigh more for the same size; moissanite is slightly less dense but close enough to require more tests. Jewelers use weight in conjunction with measured diameter and depth to flag mismatches that require additional testing.
Thermal testers measure the rate at which heat transfers through the stone. Diamonds conduct heat very fast; many simulants do not. The probe touches the gem and gives an immediate read. This test catches most cubic zirconia and glass imitations. However, moissanite and some synthetic diamonds can produce similar thermal results, so pros never rely on thermal testing alone when origin matters.
Moissanite exhibits an electrical conductivity signature distinct from that of diamond. Specialized testers measure electrical flow to distinguish moissanite from real diamonds, where thermal testing is ineffective. Experts use this test routinely when the thermal probe returns an ambiguous result. Combining electrical and thermal tests reduces the number of false positives.
Under a gem microscope, technicians map inclusions and internal growth patterns. Natural diamonds show angular crystal inclusions, crystals of other minerals, and irregular growth patterns. Lab-grown diamonds often display metallic inclusions or characteristic growth sectors from chemical vapor deposition or high-pressure high-temperature processes. Microscopic photos and inclusion maps become part of a lab report and help with long-term identification.
Advanced instruments read how the stone interacts with light at the molecular level. Raman spectroscopy identifies carbon bonding and detects stress patterns. FTIR (Fourier Transform Infrared) spectroscopy reveals the nitrogen content and helps distinguish between Type I and Type II diamonds. Photoluminescence under laser excitation can reveal defect centers that indicate synthetic growth or a natural origin. Labs use these methods to classify origin and treatment.
Experts test stones under shortwave and longwave UV lamps. Many natural diamonds fluoresce blue, green, or other colors; lab-grown stones often exhibit distinctive fluorescence patterns or phosphorescence after the light source is turned off. Observing fluorescence alongside color grading and inclusion type strengthens the identification pathway.
The refractive index of diamond equals about 2.42, producing intense brilliance and fire. Professionals use refractometers to observe optical phenomena, including doubling, dispersion, and facet patterns. Simulants often show different refraction and a telltale doubling effect when you look through the pavilion. Cut quality and facet alignment directly affect brilliance and are checked here.
Hydrostatic weighing provides a precise measurement of specific gravity. The stone is weighed in air and again submerged in liquid to calculate density. This method separates materials with close but different densities and serves as a quantitative check after the initial visual and thermal screens.
Professionals read grading reports from major labs and confirm details like carat, cut, color, clarity, and any laser inscription on the girdle. The GIA and AGS are widely trusted for consistent grading. IGI appears frequently in retail settings and is useful, but its meaning should be interpreted in context.
Technicians cross-check report numbers, plot diagrams, and microscopic images to ensure accuracy. They also verify laser inscriptions under magnification when present. Buyers should be cautious of non reputable certificates and always purchase diamonds from trusted dealers, such as Whiteflash, James Allen, and Blue Nile, which provide genuine documentation.
A typical sequence starts with loupe and weight checks, adds thermal and electrical probes, and then moves to microscope work. If doubt remains, labs run spectroscopy, hydrostatic tests, and UV evaluation. The tests used depend on the stone’s size, value, and whether origin or authenticity is a concern. Dealers and labs document findings, assign a report, and often inscribe the girdle for future ID.
If the stone is over a specific value, exhibits unusual growth patterns, or if its origin affects its price, professionals send it to a gemological laboratory. Labs provide definitive classification, treatment disclosure, and origin statements using controlled instruments and standardized protocols. Ask the lab which tests they performed and request the report number for verification.
Want to test one yourself? Start with a clean loupe, an accurate scale, and a basic thermal tester. If any result seems off, let a gemologist run the advanced checks that distinguish natural, lab-grown, and simulated diamonds.
Simulants are materials designed to resemble diamonds, but with a different chemical and physical composition. They replicate diamond sparkle and shape, allowing buyers to see a similar brilliance and fire. Some simulants occur naturally, but most are created in a laboratory today because natural examples are rare or not cost-effective. Ask yourself what matters most when you make a purchase: optical match, hardness, long-term durability, or price. That answer will point you toward a simulant or a genuine diamond certified by a lab.
Moissanite is almost always lab-produced and closely resembles a diamond in terms of brightness and sparkle. Its crystal structure gives it intense fire and brilliance, but it is doubly refractive, so a loupe or microscope will show faint double images, whereas a diamond shows a single image. A thermal conductivity diamond tester can be fooled by moissanite; therefore, many jewelers use a specialized electrical conductivity tester to distinguish between the two. Moissanite also tends to weigh slightly less than a diamond of the same diameter, so a weight-to-size ratio check helps identify it.
Cubic zirconia, also known as CZ, is an inexpensive and widely used gemstone. CZ lacks the sharp black and white contrast that defines diamond scintillation and often emits a softer, sometimes warm-colored glow under light. Over time, CZ can appear cloudy because dirt and minor surface imperfections alter how light passes through it. Under magnification, CZ shows smooth girdle edges and fewer natural inclusions than most natural diamonds. CZ is much softer than diamond and will scratch more easily.
White sapphire is a type of corundum and a genuine gemstone, yet it behaves differently in light than a diamond. It does not show the crisp contrast and bright scintillation that diamonds do. In clear water, a white sapphire loses its presence because its refractive index is lower than that of diamond, while a diamond maintains an intense sparkle. White sapphire can be a good choice for those who want a natural stone at a lower cost, but it will not fool a trained eye or specific testing tools.
White topaz is a natural gemstone that can be mistaken for a diamond by an untrained eye, but it is significantly softer and more prone to scratches. Its surface can dull with wear. For long-lasting sparkle and resistance to abrasion, opt for a more rigid material. If you already own white topaz, inspect the crown and pavilion for scratches and check the setting for looseness, since wear affects topaz more quickly than diamond.
Join thousands of engaged buyers, enthusiasts, and industry experts at PriceScope who rely on our unbiased forums, advanced tools like the Holloway Cut Advisor, and carefully vetted vendor partnerships with trusted retailers like Whiteflash, James Allen, and Blue Nile. Begin your diamond education journey today with our comprehensive guides, pricing insights, and sales-free community support. Ask specific questions, compare vendor photos and videos, and use our tools to check cut performance and price per carat.
Request a laboratory report and the corresponding lab report number. Request detailed photos and videos under multiple lighting angles. Confirm whether the girdle is laser inscribed and whether the stone had any post-growth treatments. Check return policy, warranty, and insurability. Compare price per carat to similar graded stones from trusted vendors like Whiteflash, James Allen, and Blue Nile.
A gemological report from a respected lab gives you objective data: carat weight, cut, color, clarity, and whether the stone is lab-grown. Vendor transparency, customer images, and community reviews provide valuable context for understanding prices and services. Use PriceScope forums to see real buyer experiences and get a second opinion before making a purchase.
Treat lab-grown diamonds the same way you would mined diamonds. They resist scratching, require regular cleaning, and benefit from periodic inspection for loose settings. Market resale can differ from mined diamonds due to fluctuations in supply and demand. Insure higher value pieces and keep certificates and photos on file for claims or resale.
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