6 ways to identify diamonds | Thorough explanation of the difference between real and fake
Diamond Authentication Guide
of diamondsHow to tell6 selections
of diamondsHow to tell6 selections
Thorough explanation of the difference between real and fake
From simple tests you can do at home to appraisals from specialized institutions.
We have summarized the characteristics of natural, artificial, and imitation diamonds and how to reliably determine their authenticity in an easy-to-understand manner.
"Is the diamond I received real?" "What if the ring I bought at a flea market is fake?" Have you ever felt such anxiety?
to the diamondnatural diamondIn addition to theartificial (synthetic) diamond, and made of a completely different materialimitation diamondexists. There are many things that are difficult to judge based on appearance alone, and without proper knowledge, you may be mistaken.
In this article:6 ways to tell the difference you can try at homeFocusing on this, we will comprehensively explain the reliability and limitations of each test, as well as the points at which you should seek the help of a professional to make a reliable judgment.
01
What is a fake diamond?
What is a fake diamond?
Differences between natural, artificial, and cubic zirconia
Even when we say that diamonds are "fake," there are many different truths. First of all3 categoriesLet's start by understanding it correctly. "Laboratory diamonds" and "imitation diamonds" are often confused, but they are essentially completely different things.
Natural
natural diamond
A carbon gemstone that has crystallized in the Earth's deep mantle over hundreds of millions of years in a high-temperature, high-pressure environment. Boasting a Mohs hardness of 10, it is the hardest of all natural minerals.
Lab-Grown
artificial diamond
Artificially generated using HPHT method or CVD method. The chemical composition, crystal structure, and physical properties are almost the same as natural ones. It is extremely difficult to distinguish without special equipment.
Simulant
cubic zirconia
An artificial synthetic stone made from zirconium oxide (ZrO₂). Although it looks similar to diamond, it is a completely different material with completely different hardness, refractive index, and thermal conductivity.
💎natural diamond
Natural diamonds are produced in the mantle layer approximately 150 to 200 km underground, under harsh conditions of over 1,000 degrees Celsius and over 50,000 atmospheric pressure.over 1 billion yearsIt takes many years to form. Because carbon atoms are tightly bonded in a regular tetrahedral structure, it has the highest hardness among minerals (Mohs hardness: 10).
Natural diamond formation process
🌋 deep mantle High temperature/high pressure environment
→
⏳ over 1 billion years Time required for crystallization
→
💎 natural diamond Mohs hardness 10
Volcanic activity (kimberlite pipe eruption) brings it to the surface and it is mined.
As a characteristic of natural diamonds, when observed with a magnifying glass,Minute inclusionsThe following are points that are often seen. This is evidence of growth in a natural environment, and completely intact ones are rather rare.
🔬artificial diamond
Man-made diamonds (synthetic diamonds, lab-grown diamonds)HPHT method (high temperature and high pressure method)orCVD method (chemical vapor deposition method)Industrially manufactured by.
Two main synthesis methods
🏭 HPHT method Grown with high temperature and high pressure press
／
⚗️ CVD method Deposition from methane gas
Either way, the chemical composition (pure carbon) and crystal structure are identical to natural diamonds
Lab-grown diamonds are natural andSame chemical composition (C), same crystal structureTherefore, their physical properties such as hardness, refractive index, and thermal conductivity are almost the same. Therefore, it is extremely difficult to tell them apart, not only with the naked eye, but also with regular loupe inspection.Dedicated analyzerwill be required.
💡 Points you need to know
Lab-grown diamonds are not "fake" but "real" diamonds. The only difference is that it is not natural, and it does not mean that it is inferior in quality as a gemstone. However, due to the environmental concerns caused by methane and the rarity of natural diamonds, diamonds are not widely used as decorative items, and are mainly used for industrial purposes.
✨Cubic zirconia | Representative of imitation diamonds
Cubic zirconia (CZ) is a crystal that is artificially synthesized from zirconium oxide (ZrO₂). What is a diamond?Completely different chemical composition and crystal structureIt is a so-called "imitation stone (diamond simulant)" that has a
| characteristics | natural diamond | artificial diamond | cubic zirconia |
|---|---|---|---|
| chemical composition | C (carbon) | C (carbon) | ZrO₂ |
| mohs hardness | 10 | 10 | 8〜8.5 |
| refractive index | 2.42 | 2.42 | 2.15〜2.18 |
| specific gravity | 3.52 | 3.52 | 5.6〜6.0 |
| thermal conductivity | very high | very high | low |
| price range | expensive | About 30-50% of natural | very cheap |
The specific gravity of CZ is about 1.7 times that of diamond, so even for the same carat weight,Feels a little heavy when you hold it in your handIt is characterized by Also, due to the difference in refractive index, the dispersion (fire) of light is stronger than that of diamond, and the iridescent glare tends to be more noticeable.
⚠️ Attention
In addition to CZ, there are several other materials used to imitate diamonds, such as moissanite (SiC) and white sapphire. especiallyMoissaniteBecause its thermal conductivity is close to that of diamond, it is mainly determined using a simple tester.
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02
6 ways to tell the difference between real and fake diamonds
From here on, you can easily try how to tell the difference at home.sixLet me introduce you. All require no special equipment, but each test has different reliability levels and limitations.Don't make decisions based on just one test, combine multiple testsThat's important.
📌 Key points for reading
We give each test a "confidence badge." Just to the lastDistinguishing between natural diamonds and CZ (imitation stones)Reliability in terms of perspective. Neither method is compatible with distinguishing between natural and artificial (synthetic) diamonds.
1
breathe
One of the simplest and most famous tests is the "breath test" (cloudy test). of diamondsHigh thermal conductivityThis method does not require any special tools.
💨 Take a breath and say “Haa~”
Spray
➜
Spray
🔍 How to get rid of cloudy weather
observe
observe
💎 Genuine (natural/artificial)
✨
cloudy1-2 secondsdisappears instantly.
Heat diffuses quickly due to high thermal conductivity.
Heat diffuses quickly due to high thermal conductivity.
⚠️ CZ, glass, etc.
🌫️
cloudy3-5 seconds or moreremain.
Due to its low thermal conductivity, water vapor does not dissipate easily.
Due to its low thermal conductivity, water vapor does not dissipate easily.
💡 Limitations of this test
Moissanite also has high thermal conductivity, so it is difficult to tell the difference just by using a breath test. Also, it is easily affected by the size of the gemstone and room temperature, and it may be difficult to tell the difference with small stones. Please use it only as an "initial screening".
2
put it in the refrigerator
The "refrigerator test" has become a hot topic on social media. This is an advanced version of the breath test, which makes the results easier to understand by increasing the temperature difference.
🧊 in the fridge
Cool for 2-3 minutes
➜
Cool for 2-3 minutes
🤲 Take it out
leave at room temperature
➜
leave at room temperature
🔍 Cloudy or not
Check how it disappears
Check how it disappears
💎 Genuine (natural/artificial)
✨
Even if there is a slight condensation the moment you take it out,Disappears almost instantly. The stone itself adapts to the temperature quickly.
⚠️ CZ, glass, etc.
💧
Condensation and cloudiness on the surfacewill remain for a while. It stays cool to the touch for a long time.
⚠️ Handle with care
Sudden temperature changes can damage the metal parts and adhesives of your jewelry. It is best to avoid this, especially with delicately crafted items such as antique jewelry or pavé settings. Do not use the freezer (below freezing).
3
Check the refractive index of light
The refractive index of diamond is2.42It is extremely high and reflects and disperses light internally. This property is used to check the pattern of how light shines.
🔦💎🌈
Shine a bright light source (such as a penlight) on the stone,
How to shine from withinandRainbow color dispersionobserve
How to shine from withinandRainbow color dispersionobserve
💎 real diamond
🤍
Sharp white to gray shine(brilliance) is the main focus. The rainbow-colored fire scatters discreetly and elegantly.
⚠️ CZ Moissanite
🌈
strong iridescent glarestands out. CZ has a higher dispersion value than diamond and tends to produce seven flashy colors.
💡 Tips for distinguishing
The brilliance of a diamond is characterized by a sharp white flash. If the rainbow colorsToo flashy/too glaringIf you feel that way, it may be CZ or moissanite. However, the appearance will vary depending on the quality and size of the cut, so please use this as a reference only.
4
Use oil-based pen and water
diamond isLipophilicity (easily compatible with oil)I have There are two testing methods that take advantage of this characteristic.
Test A: Oil-based pen test
🖊️💎
on the stone surface (table surface)permanent markerDraw a line.
real diamond → The ink transfers smoothly and allows you to draw continuous lines.
CZ, glass, etc. → Ink is repelledintermittent
real diamond → The ink transfers smoothly and allows you to draw continuous lines.
CZ, glass, etc. → Ink is repelledintermittent
Test B: Water drop test
💧💎
⚡ Reliability: low
on the stone surfacesmall water dropletsdrop.
Real diamond → water dropletsstay round(hydrophobic)
CZ, glass, etc. → Water dropletsspreads quickly
Real diamond → water dropletsstay round(hydrophobic)
CZ, glass, etc. → Water dropletsspreads quickly
⚠️ There are limits
Accurate results will not be obtained if the stone surface is dirty or coated. Also, it is easy to try out loose stones, but it may be difficult to try them out if they are set in a ring or the like. After testing, please gently clean it with a mild detergent.
5
shine a black light
Approximately 25-35% of natural diamonds can bepale fluorescentIt has the property of emitting This is a method to check this "fluorescence".
🔮💎💙
in a dark roomLong wave UV (black light)irradiated onto the stone.
If you see blue-white fluorescence, there is a high possibility that it is a natural diamond.
If you see blue-white fluorescence, there is a high possibility that it is a natural diamond.
💎 natural diamond
💙
Approximately 25-35% natural diamondspale fluorescentemits. The strength varies depending on the stone.
⚠️ CZ
💛
No fluorescence or if it doesyellow/greenIt is often fluorescent.
💡 Important notes
natural diamond65-75% show no fluorescence. Just because there is no fluorescence, it cannot be determined that it is a fake. Conversely, some synthetic diamonds can exhibit unique fluorescence patterns. Please limit this test to the extent that it will be helpful if you pass the test.
6
Seeing through the lines drawn on paper
"Read-through test (watermark reading test)" takes advantage of diamond's high refractive index. You can try it out by simply placing a bare stone on the paper.
📝 on white paper
draw a straight line
➜
draw a straight line
💎 stone on the line
put the table face down
➜
put the table face down
👁️ Peeking from above
Check if the line is visible
Check if the line is visible
💎 real diamond
⬜
Because the refractive index is high and light is reflected in a complicated manner,I can't see any lines。
⚠️ CZ, glass, etc.
〰️
Because the refractive index is low and light passes through,The lines are faintly visible。
💡 Tips to improve accuracy
This test is only valid for loose stones. You cannot try it on a ring or necklace. Additionally, diamonds that are cut too shallow may allow light to pass through, resulting in visible lines. This is the most reliable test for round brilliant cuts.
📊Compare 6 methods in list
| Test method | what you need | Reliability | Distinguishing from CZ | Distinguishing from composite |
|---|---|---|---|---|
| ① Breathe | None | ★★★☆☆ | ◯ | ✕ |
| ②Put it in the refrigerator | refrigerator | ★★★☆☆ | ◯ | ✕ |
| ③Refractive index of light | pen light | ★★★☆☆ | ◯ | ✕ |
| ④Oil-based pen and water | Oil-based pen/water | ★★☆☆☆ | △ | ✕ |
| ⑤Black light | uv light | ★★☆☆☆ | △ | ✕ |
| ⑥Watermark reading | paper/pen | ★★★★☆ | ◎ | ✕ |
⚠️ “Natural vs. artificial” cannot be determined by any method
All of the above six methodsDistinguishing between “diamonds (natural/artificial)” and “imitation stones (CZ, glass, etc.)”is valid for. Photoluminescence analysis and other methods are used to distinguish between natural and artificial diamonds.Specialized equipment requiredIt is. If you want reliable results, consider the methods presented in the next chapter.
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03
What to do if you're worried about whether the diamond is real
If you feel that it may be suspicious during the home test, orReliable proof requiredIn such situations, seek professional help. Here, we will introduce three ways to safely obtain diamonds.
Buy from a trusted store
Official jewelry stores and brand stores have clear procurement routes and thorough quality control. Compared to flea market apps and personal sales, the risk of counterfeiting is greatly reduced.
Get a certificate issued
Appraisal reports (grading reports) issued by appraisal organizations such as GIA, CGL, and AGT contain not only natural certification but also 4C evaluations, which serve as support for asset values.
Have it appraised by a specialized agency
If you are concerned about a stone you already have, you can take it directly to a gemstone appraisal agency. Prices range from a few thousand yen, and we can accurately distinguish between natural, synthetic, and imitation products.
🏪Buy from a trusted store
The most reliable countermeasure against counterfeiting isEliminate risk at the purchase stageThat's it. The characteristics of a reliable store include the following:
- GIA, CGL etc.Third-party appraisal report included as standardare doing
- Clear return/exchange policy and post-purchase guarantee
- Persons with gemological qualifications (GG, FGA, etc.) are employed.
- Belongs to an industry organization (Japan Jewelry Association, etc.)
Especially if you buy online.Can I check the certificate number?Make sure to check if there are real photos and videos posted, and if the reviews are reliable.
📜Get a certificate of authenticity issued at the time of purchase
A diamond grading report is an important document that proves that the stone is a natural diamond and contains the 4C evaluation of carat, cut, color, and clarity.
Major appraisal institutions
🌍 GIA The world's largest appraisal agency
No.1 in international reliability
No.1 in international reliability
🇯🇵 CGL Central Gem Research Institute
Largest domestic company
Largest domestic company
A "certificate of authenticity" and a "certificate of identification" are different things. The certificate comes with a 4C evaluation, and the certificate only identifies the type of gemstone (natural/synthetic).
💡 Difference between “certificate” and “certificate”
Grading Report:For diamond only. Includes 4C quality assessment.
Identification Report: Applicable to all jewels. The purpose is to identify the name of the gemstone, whether it is natural or synthetic. If you want to know the authenticity of a stone you already have, please request a ``Certificate of Authenticity''.
🔬Have it appraised by a specialized agency
If you are concerned about the authenticity of a stone you already own, your best bet is to take it directly to an appraisal agency. Many institutions also accept items brought in by individuals.
Appraisal process
📞 STEP 1 Reservations/Inquiries
→
🏢 STEP 2 Bring in or mail
→
🔬 STEP 3 Appraisal/inspection
→
📄 STEP 4 Receiving results
- Estimated cost: Approximately 3,000 to 6,000 yen just for identification, 5,000 to 15,000 yen with certificate (varies depending on stone size and institution)
- Required number of days：Same day to about 1 week (depending on congestion)
- Tips on what to bring:If you have the receipt and accompanying documents from the purchase, please bring them with you◎
💡 You can also take advantage of the free appraisal at the purchasing store.
Even if you have no intention of selling, there is a way to get a second opinion on the authenticity by using a free appraisal at a major buying store. However, since the purchasing store is not an appraisal agency,No official certificate issuedPlease note: Please use this information only as reference information.
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Finally
We have introduced how to identify diamonds, but none of the methods can be done at home.A simple test to spot “imitation stones (CZ and glass)”and is not a panacea.
In particular, even a professional gemologist can distinguish between man-made diamonds and natural diamonds.Not possible without specialized analytical equipmentIt is. If you want to know the true value of your precious jewelry, don't hesitate to consider having it appraised by a professional organization.
Correct knowledge is the best weapon to protect your precious jewelry.
We hope this article will help you have a safe encounter with diamonds.