Ultimate Diamond Buying Guide

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Getting Started

Ultimately, you want a diamond that will look great in its setting. That means buying a diamond that appears colorless and flawless and has great sparkle.

What's the most important thing you can do to accomplish this? It may sound obvious, but you need to make sure you can see your diamond before buying it. Don't just trust a diamond's grade report. Without seeing the actual stone, you have no way of knowing how well it really performs.

If you're shopping at a brick-and-mortar store, have the jeweler show you your diamond carefully. View it from different angles under both indoor and outdoor light. Check how it looks against the type of metal setting you'd like.

If you're diamond buying online, choose a vendor with a large selection, online videos of each stone, and viewing tools. You can view your stone in 360°, zoom in and out, and see what it will look like in various settings.

Custom jewelers are another great option. They can help you through the entire engagement ring process, including choosing the perfect diamond center stone for a unique ring design.

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Summary: Four Steps to Diamond Buying

Step 1: Determine Your Budget

Before you even start shopping, you'll need to set your budget. Diamonds are expensive, so a budget will ultimately help you decide what you want.

You probably already know that diamonds are expensive, but you might not know just how expensive they are. Keep in mind, though, that you can find a nice diamond within most budgets. However, you may have to compromise.

For example, lab-made diamonds are a nice alternative to mined diamonds. Although they have the same beauty and durability, they cost about 30% less. So, buying a lab-made diamond will save you some money.

Step 2: Pick a Diamond Shape

Next, figure out what shape best suits your style. Round brilliant diamonds are the most popular, but other shapes cost less. You have many choices: ovals, pears, squares, rectangles, and even triangles. Many diamond shapes even look larger than a round of the same carat weight.

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If you're not sure which shape is best for you, check out our guide to diamond shapes.

Step 3: Find the Best Color and Clarity Grades for Your Ring

After you pick the shape, find the color and clarity grades that will give you the best deal. You'll probably want a diamond that appears colorless or white in the setting, rather than off-color. You'll also want a diamond that appears flawless to the eye from a normal viewing distance (about 6 inches away).

Colorless and flawless diamonds receive the best grades — and command the highest prices. Just remember, you're looking for the grades that will get you the best deal. The color grade you choose will depend on whether you want a ring made of yellow gold, rose gold, or white gold or platinum, as well as the shape and setting style you want. The clarity grade you pick will also depend on the diamond shape.

Step 4: Find the Best-Cut, Largest Diamond

Finally, it's time to start browsing! By narrowing certain cut parameters, you'll be able to find a diamond that's extra sparkly. Then, you just find the sparkliest, biggest diamond within your budget.

Sounds simple, right? Now, let's get into the details.

Diamond Budget and Price

Of course, the price of a diamond is going to be one of the major factors in deciding what you buy.

Many people have expectations about the diamond that they'll buy (or receive), especially when it comes to carat weight. In reality, though, if you want the best diamond your money can buy, carat should be the last item you consider.

Still, to give you an idea of how much a diamond costs at different carat weights, look at the following chart.

Keep in mind that these are averages. You might find diamonds with these qualities at higher or lower prices. We've selected these specific diamond properties (shape, color, clarity, and cut) based on our recommendations for a round diamond in a white gold solitaire ring. Therefore, these prices aren't universal. Diamonds with different properties will have a different range of prices.

Lab-Made Diamonds

With new technology driving down manufacturing costs, lab-made diamonds are becoming less expensive and more popular. While these diamonds don't retain their value, mined diamonds don't either. You'll find that trying to sell a diamond, whether mined or lab-created, won't get you anything near the price that you paid for it.

At prices about 30% cheaper than mined diamonds, lab-made diamonds are much more affordable than their natural counterparts. They also have the same beauty and durability as mined diamonds, so they're indistinguishable unless you look at their grade certificates. Buying a lab-made diamond can free some room in your budget for some upgrades, like a higher carat weight.

Both these round brilliant diamonds have G color, VS2 clarity, and Excellent cuts. The 1-ct mined diamond costs $5,030. For the same price, you could purchase a 1.58-ct lab-created diamond.

Diamond Alternatives

Of course, if a lab-made diamond is still too expensive, there are other alternatives that mimic a diamond's beauty and durability.

Moissanite is one of the most popular. This lab-grown gem shows beautiful brightness and colorful flashes, very similar to a diamond. In fact, non-experts have trouble telling moissanite apart from diamond.

If you prefer a mined gemstone to a lab-made one, bear in mind that nothing will quite imitate the look and durability of diamond. Although white sapphires are popular lookalikes, their sparkle will never match that of diamonds. Natural zircons (not to be confused with synthetic cubic zirconia) may come the closest in appearance, but can chip and wear easily.

Ring Styles

Next, consider the style of ring you'd like. Solitaires are sweet and simple, while popular halos provide extra sparkle. Some prefer side stones or intricate vintage settings.

Not sure what you're looking for? Check out our guide to engagement ring settings.

Some online vendors, like James Allen or Blue Nile, allow you to choose a ring type and then virtually set one of their loose diamonds in it. So, you can actually preview what your setting and stone will look like together. If you're shopping at a brick-and-mortar store, ask to see examples of different ring styles with set stones like yours.

Should You Buy the Diamond or the Setting First?

Unless you're purchasing a ready-made diamond ring, you'll have to decide which component you want to buy first: the stone or the ring. You can do either, but each choice offers some advantages.

If you purchase your center stone first, you'll know its exact dimensions. This is important if you're having a setting custom made, so the jeweler can take into account any unique aspects of the diamond. You'll also know the stone's exact color, so you can choose any accents appropriately. Finally, since the center stone is likely the most expensive item in your budget, you'll be sure to get the stone you want. Then, you'll know how much you have left for the mounting.

On the other hand, if you have a very specific ring design in mind, you may not want to just use "what's left of the budget" for the setting. If you're working with a custom jewelry maker, they can help design a ring and then search for the best diamonds for your project, within your budget.

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Diamond Shapes

Next up, you'll want to pick a diamond shape. If you're buying a diamond for your partner, you probably already have a clue about the shape. (If not, go get one right now!)

Although round diamonds are the standard for engagement ring stones, many people prefer a different shape, perhaps one that better reflects their personality or style. Plus, fancy shapes (non-round shapes) are less expensive than rounds of the same carat weight with identical properties. They often appear bigger than rounds, too.

Princess, Cushion, and Radiant Shapes

Princess-cut diamonds are the most popular fancy shape. Their square outline gives the ring a strong geometric look. For a softer and more traditional look, consider a cushion-cut diamond. Or, if you want something just a little less starkly geometric than a princess, a radiant-cut diamond makes an ideal choice.

Oval, Pearl, and Marquise Shapes

Oval shapes provide a nice twist on the traditional look. Their elongated shapes make them appear larger than rounds. Plus, when oriented along the direction of your finger, an oval will make your hand appear longer and slimmer. Pear shapes have a similar effect but with a unique asymmetry. Marquise shapes take the long-and-slim look to a whole other level. They actually have the largest face-up appearance of any diamond shape.

Emerald and Asscher Shapes

If you prefer a broad flash of light to a sparkly brilliance, you'll probably like an emerald or asscher-cut diamond. Although more commonly used for emerald gemstones (and named after them), the emerald cut is a step cut that shows off more subtle aspects of a diamond's beauty. Another type of step cut, asscher-cut diamonds have a more square profile and deeper depth. Although they have the smallest face-up area, they have a unique geometry and vintage flair unmatched by any other shape.

Heart and Trillion Shapes

For the sentimental, heart shapes are another great option. These diamonds have a special meaning for their wearers. (They also make a great way to match a tattoo!)

Uncommon choices, trillion shapes will make unique center stones. Their interesting geometry will always stand out from the crowd.

Diamond Buying and the Four Cs

After you've selected a shape, you can start considering the Four Cs: clarity, color, cut, and carat. Any diamond you buy should come with a grading report with grades for clarity and color and a carat weight measurement. Round diamonds will also have a cut grade. (Fancy shapes don't receive cut grades from gem labs).

While these grades don't give you the full picture of a diamond's quality, they can come pretty close. So, when you're buying a diamond, you must understand these four properties and how they impact your diamond's quality and price.

We'll start with what might be the most confusing to a first-time buyer: clarity.

Diamond Clarity

Clarity grades range from Flawless (F) to Included (I), with several grades in between. The full list (from highest to lowest) is F, IF, VVS1, VVS2, VS1, VS2, SI1, SI2, I1, and I2. (Some grading labs might also use SI3 and/or I3).

Flawless and Internally Flawless

So, Flawless sounds good, right? Well, it might until you see the price tag. At the top of the clarity scale, Flawless (F) and Internally Flawless (IF) diamonds command extra-high prices.

However, the grade "Flawless" doesn't mean that these diamonds have no flaws. It just means that the flaws that they do have are smaller than what we can see with the microscope used for grading clarity.

Diamonds in this clarity range will certainly appear flawless to the naked eye, or "eye-clean," but they'll also be much more expensive than necessary.

Both these diamonds have the same color and cut grades and the same carat weight. Both appear clean to the naked eye. However, the F clarity stone costs $5,570. The VS1 clarity stone costs $3,930.

Very, Very Small Inclusions

Next on the clarity grading scale is VVS1 and VVS2, which stands for "Very, Very Small" inclusions. These diamonds contain microscopic flaws. While they certainly appear flawless to the naked eye, these diamonds are still quite expensive.

Very Small Inclusions

In the VS clarity range, diamonds start becoming more affordable but will still appear flawless to the naked eye. In most diamond shapes, VS clarity diamonds will be completely eye-clean. Flaws in these stones require an expert with a 10x magnification loupe to see them, so it's unlikely you'll ever spot an inclusion in one of these diamonds.

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The exception is in emerald and asscher cuts. These step-cut diamonds act like a window into a series of mirrors. Any flaw large enough to see will be visible. Even then, VS1 clarity diamonds will always be eye-clean. Most VS2 clarity emerald and asscher-cut diamond will be eye-clean, too. However, larger sizes (3+ carats) will tend to show more eye-visible flaws.

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Small Inclusions

In the SI clarity range, diamonds of any shape might have eye-visible inclusions. However, there's still a significant difference between SI1 and SI2 clarity grades.

Nearly every SI1 clarity diamond will be eye-clean. Although these diamonds have small flaws, most aren't readily visible. On the other hand, SI2 diamonds have larger or more numerous flaws, so more of these will have visible imperfections.

Budget constraints might lead some shoppers to consider SI diamonds. Others might decide to sacrifice clarity in order to buy a larger carat stone. Whatever the reason, before you settle on an SI stone, make sure you're OK with a small visible flaw.

Many people can make peace with a small flaw if it saves them hundreds of dollars. In fact, the type of imperfections that we're talking about with SI stones are hard to spot if you don't know they're there. If a non-expert closely examines your ring, they might be able to find it. (Most likely, not many people you know will look at your ring from six inches away).

Included

Diamonds in the I clarity range almost always have large, numerous, visible flaws.

In general, we recommend avoiding I clarity diamonds. Stones in this range have a chance of breaking, since large flaws can create weak points. (Diamonds are famous for their hardness, but that only protects them from scratches, not breaks). With so few eye-clean diamonds in this range, you might be unhappy with your purchase. If you need to economize, stick to an SI clarity diamond and choose a lower carat weight rather than risk a broken stone.

Clarity Recommendations

Remember, in terms of clarity, what's important when diamond buying is that the stone appears flawless. So, if your budget allows it, we recommend sticking to a VS2 or SI1 clarity grade. If you choose a higher clarity grade, you're paying more for something that you'll never notice. You can also find a great diamond with an SI2 clarity, as long as you search carefully.

The only major exception to this recommendation is for emerald and asscher cuts. If you choose these shapes, stay with VS1 or VS2 clarity.

Inclusions to Avoid

If you're looking at diamonds in a clarity grade that might be visibly flawed, always avoid large, dark inclusions near the center of the diamond. These are always the most readily visible.

If you're shopping at a brick-and-mortar jeweler, hold the stone about 6 inches from you and see if you can notice any flaws.

Online vendors may have tools that let you magnify or zoom out when you view stones in their inventory. Take a good, closeup look at one of their stones and make a mental note of any large flaws and their location. Next, zoom out to normal (x 1) magnification. If you can still spot the flaws, the diamond's probably not eye-clean. If you can't, you might have an eye-clean stone.

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Diamond Color

Next, you'll narrow your diamond color choices. Most colorless (white) diamonds on the market have color grades of D through M. In this grading system, D color diamonds have the least color. Grades further down the alphabet show incrementally more color. (Fancy color diamonds, like pinks and blues, have their own distinct color grading system. We won't cover those in this article).

With clarity, it doesn't matter if the diamond you're buying is actually flawless. Similarly, with color, it doesn't matter if the diamond is actually "colorless." When diamond buying, you just need to stick to the ones that will appear colorless.

Did you know that diamond color grades don't refer to the diamond's face-up appearance? Diamond graders actually grade color from a side view, even though you'll almost always view the stone face up once it's set in a ring. That means that some diamonds might have slightly more color face up and some might have slightly less. It also makes it especially difficult to tell a diamond's face-up color. Take our quiz and try it yourself.

Let's take a look at the different color grades.

Colorless Diamonds: D, E, and F

At the top of the color grade scale are "colorless" diamonds. These diamonds will definitely appear bright and colorless. However, they come with a hefty price tag.

Before you get your heart set on a diamond in the colorless range, you should realize it's almost impossible to distinguish these diamonds, face up, from G or H color diamonds.

Plus, for those who prefer the aesthetic of yellow or rose gold to white gold or platinum, the color of the metal will actually reflect through the stone, making it appear to have more color. So, if you choose a diamond in the colorless range, we recommend using a setting with white gold or platinum prongs. This will better show off the high color grade.

Compare how this 1.01-ct, round diamond with F color and SI2 clarity looks when set in white gold prongs versus yellow gold prongs.

Near-Colorless Diamonds: G, H, I, and J

In most cases, a near-colorless diamond is actually a better buy than a true colorless stone. G and H color diamonds will look bright white. I color diamonds will still look good, too.

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While J color diamonds will show a little color in a white gold setting, they'll look great in yellow or rose gold.

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Since near-colorless diamonds offer major savings compared to colorless ones, without losing any of their beauty, we recommend buying diamonds in this color range.

Faint Diamonds: K, L, and M

Lower color grades begin to show more noticeable color. Nevertheless, these faint colored diamonds can still look great in colored metal settings.

Since many antique diamonds had noticeable color, consumers have come to associate faint color in diamonds with vintage flair. If you like this style, purchase a modern faint diamond and pair it with a vintage-style setting.

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Diamond Color Recommendations

If you want your diamond to appear colorless, then the type of setting and metal you select makes a big difference. Since your eye automatically compares adjacent colors, side stones and metal colors affect how colorless your diamond will look once set.

For diamond halo or side stone settings, check the details of the accent color grades. These are often (but not always) G/H or F/G. Generally, choose a center stone and accents with the same color grade, so your center diamond doesn't look off color. Some halo or side stone settings place the accents farther away from the center stone. In these cases, you could opt for a center stone color grade a little lower than that of the accents.

For solitaire rings or rings with pavé bands with accents farther from the center stone, the metal color matters more than the accent colors. In white gold or platinum, stick to an I color stone or better for the best deal. In yellow or rose gold, you can drop down into the "faint" color range and still have a great ring.

Diamond Shape and Color

Of course, these recommendations are best suited for round diamonds. Rounds actually show less color than other shapes. So, if you've picked a fancy shape and want your stone to appear colorless, tweak your search to include higher color grades.

For princess, emerald, and asscher cuts, you'll want an I color or better. Other fancy shapes show more color, so you might want to add H color to your search parameters.

When examining non-round loose diamonds, check to see if they have color concentrations in any corners. Diamonds with ends the same color as the center will look best.

Diamond Cut Quality

Now, we come to the most important of the Four Cs: cut quality. Why is the cut so important? In part, because it actually affects how you perceive the other Cs: clarity, color, and carat.

In a well-cut diamond, flaws are more difficult to spot. Since there's more brilliant white light coming through the diamond, the color grade becomes less important. Also, thanks to that brightness, the stone actually appears larger. So, pay special attention to the cut when diamond buying.

Of course, the best cut quality varies by diamond shape. (Keep in mind that only rounds receive cut grades on their reports). We'll discuss cut quality for each shape in this section.

Cut Quality and Performance

Better cut quality gives the diamond better performance.  Performance covers three basic qualities: brilliance, fire, and sparkle.

• Brilliance refers to the white light return, which makes the diamond appear bright white.
• Fire, or dispersion, refers to the flashes of color you see in a diamond.
• Sparkle refers to the pattern of tiny flashes of white light in contrast to black spots and how it scintillates in the stone.

Ultimately, a stone's performance is what should matter most when you're diamond buying. Each diamond will perform somewhat differently. Some will show more fire, while others will have more brilliance. Sparkle patterns differ tremendously among different shapes, too.

To find the best diamond, after fine tuning your search by color, clarity, and carat, you'll have to look at your search results and decide which stone performs best.

Round Brilliant Diamond Cut Quality

When you're searching for round diamonds, stick to cut quality grades of "Excellent" or "Ideal." "Very Good" cut quality just isn't all that great. Take a look at this side-by-side comparison.

Both these diamonds have J color, but the Very Good cut appears more yellowish than the Excellent cut.

While focusing on the cut grade really helps find diamonds that perform well, you should narrow your search even more.

Table Percentage and Depth Percentage

Some online vendors allow you to narrow your search parameters by table percentage and depth percentage.

• The table percentage indicates how large the top facet is compared to the overall width of the diamond.
• The depth percentage is the diamond's diameter divided by its depth and can indicate how deep or shallow the stone is.

Since a round cut is specifically designed to provide the best play of light, narrowing these parameters can get you a better selection of diamonds with great cut quality.

For round diamonds, the table percentage should be between 54 and 57%. The depth percentage should be between 59 and 62.6%.

Diamonds with small tables let less light in, which makes the diamond less bright. Similarly, diamonds that are too deep or too shallow return less light to your eye. This makes them less brilliant and sparkly.

Please note, however, that a large table doesn't make a diamond perform better. A large table will actually decrease a stone's dispersion, and the odd balance between table and crown will just make the diamond not look right.

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Hearts and Arrows

Some diamond buyers want "the best of the best," and for some, that means hearts and arrows. In most cases, a hearts and arrows diamond will be a great option with a fantastic cut. However, you can find a diamond with a cut that performs just as well but doesn't have a good hearts and arrows pattern.

That's because the hearts and arrows pattern arises from a diamond's symmetry, rather than its cut quality. A perfectly symmetrical, well-cut diamond will have a beautiful set of hearts and arrows. With slight asymmetry, the hearts and arrows are lost but the cut quality can still be amazing.

Both of these 1.01-ct diamonds have stellar clarity and color grades. Both look wonderful, but the hearts and arrows costs $11,160, while the Excellent cut costs $8,590.

Unless it holds a special meaning for you, don't pay extra for a hearts and arrows diamond. However, if you do plan on buying a hearts and arrows diamond, check out our article to ensure you know what you're paying for.

Cut Quality in Other Diamond Shapes

Diamonds with non-round shapes don't receive cut grades. This makes narrowing your search for these stones a little more difficult. However, you can still eliminate some inferior cuts with depth and table percentages. Then, you'll have to consider the diamond's shape appeal. Simply put: just how much do you like a particular stone's shape?

Asscher-Cut Diamonds

In asscher-cut diamonds, the most important performance aspect is the play of light and dark as the diamond moves. The differences in this play of light are a matter of preference. Still, you should avoid stones that go completely dark at certain angles or those with facets that never seem to reflect light.

For shape appeal, look at the cut corners and make sure they're regular and symmetrical and neither too large nor too small.

The ideal depth for an asscher-cut diamond is between 61 and 68%. The table should be from 60 to 68%.

Cushion-Cut Diamonds

When buying a cushion-cut diamond, you'll have to decide whether you prefer the "chunky" look or a "crushed ice" appearance. This is really a matter of preference and doesn't impact its quality.

You should also consider whether you want a square or rectangular cushion. Square cushions should have a length-to-width ratio of 1.00-1.05, while rectangular ones should be about 1.15-1.20.

For shape appeal, keep in mind that a cushion's shape can range from nearly round to nearly square. Most consumers prefer one with nicely rounded corners and slightly curved sides.

Finally, limiting the depth to 61-68% and the table to under 68% will help you find a nice one.

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Emerald-Cut Diamonds

Similar to asscher cuts, the appeal of emerald-cut diamonds lies in the sparkle of light and dark as the stone moves. Avoid ones with facets that never light up or with large areas that go dark at once.

Check the cut corners for symmetry and size. Corners that differ in size will look noticeably off, and those too big or small for the stone won't look good.

Next, consider the diamond's length-to-width ratio. Most consumers prefer a ratio of about 1.45. However, some prefer shorter stones with a ratio of 1.30, while others like elongated ones of 1.60.

Finally, you can limit the depth to 61-68% and the table to 60-68%.

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Heart-Cut Diamonds

Shape appeal is very important in a heart cut. If you're looking for a heart shape and it just looks odd, that's probably because it's off shape.

Look for symmetry between the two halves and a distinct cleft between them. You'll also want well-rounded lobes and a distinct point.

Consider the length-to-width ratio, too. A ratio around 1.00 is ideal, but anything in the range of 0.90-1.10 will still look good. Outside this range, the diamond will appear either chubby or skinny.

Finally, limiting the depth to 56-66% and the table to 56-62% will help you find a heart that will perform very well.

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Marquise-Cut Diamonds

Shape appeal is also very important in a marquise cut. You'll really notice even a slight asymmetry in the outline of a diamond with this long and skinny shape.

Look closely at the diamond's outline. Check that the wings (near the tip) and belly (near the center) are neither too bulgy nor too skinny.

Next, look at the belly region and ensure that there isn't a large, black "bowtie" area.

You might also want to limit the length-to-width ratio in this diamond shape. Most prefer marquise diamonds with a ratio of 1.7 to 2.2.

Finally, limiting the depth to 58-62% and the table to 53-63% will help you find a great marquise diamond.

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Oval-Cut Diamonds

In an oval-cut diamond, watch for the bowtie effect. In a poorly cut oval diamond, you'll see a band of black facets across the middle of the stone. You'll want to look for a diamond with a bright middle section, instead.

The 1.00-ct, H color oval has a bright middle, while the 1.01-ct, F color oval has a noticeable dark bowtie.

Of course, shape appeal is also important. Try to avoid ovals that are pill-shaped, asymmetrical, or have any odd bulges.

You might prefer a particular length-to-width ratio, too. Most consumers prefer ovals in the range of 1.3 to 1.5.

Finally, limit the depth to under 68% and the table to 53-63% to find the best oval.

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Pear-Cut Diamonds

Finding a pear-cut diamond with good shape appeal can be difficult. If the shape looks off, skip it and find another.

First, look for symmetry between the two halves. Next, make sure that the rounded end is a semicircle without any flat areas or bulges. The other end of the diamond should taper nicely to a distinct point, without being too flat or too curved. This area often has "bulging wings," which hide weight. Unfortunately, the extra carat weight doesn't help the oval look better. It will just make the stone cost more.

Like ovals, pears also have a bowtie effect. Avoid any stone with a noticeable region of dark facets across its middle.

You might also want to limit a pear's length-to-width ratio. Most consumers prefer a ratio between 1.45 and 1.75. However, you'll find many shorter and chubbier ovals for sale, which fall outside this range.

Finally, limit the depth to under 68% and the table to 53-65%.

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Princess-Cut Diamonds

Variations in a princess-cut diamond can create a stone with a "chunkier" sparkle or one with smaller "bits" of sparkle. Don't worry too much about this distinction. Just choose a diamond that you like.

When shopping for a princess cut, shape appeal is very simple: look for a square. Corners should be sharp and sides straight.

A square princess cut will have a length-to-width ratio of 1.00, of course. However, some are just rectangular enough to look a bit off-shape. Limit the ratio to under 1.05 to find a good shape.

Limiting the depth to 68-75% and the table to 69-75% will also help you find a nice princess cut.

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Radiant-Cut Diamonds

Combining the outline of an emerald cut with brilliant facets, the radiant cut is a recent invention. Fortunately, like a princess, finding a nice radiant is straightforward.

Symmetry is key. Check the cut corners for symmetry. Each should be the same size and at the same angle. They shouldn't be so large that the stone looks like a weird octagon or so small that they're not noticeable.

Most consumers prefer a length-to-width ratio of 1.15-1.35. For square radiant cuts, keep the ratio under 1.05.

Finally, limit the depth to under 67% and the table to 61-69% to find a good radiant.

Trillion-Cut Diamonds

The trillion cut is all about shape appeal. Find a symmetrical triangle, unless you're going for a bold asymmetrical look. Each side should be the same length, and the angles should be equal.

Some consumers prefer softly rounded sides, while others like the stark geometry of a straight-edged triangle. Either way, make sure your stone has no odd bulges. Each side should be equally flat or curved.

Limiting the length-to-width ratio to below 1.10 will help you find a symmetrical stone. In a well-cut trillion, the depth should be between 32 and 48% and the table between 50 and 70%.

Other Diamond Buying Considerations

Here are a few more things you might consider when diamond buying: the grading laboratory, polish and symmetry, and fluorescence.

Grading Laboratory

Different grading laboratories can have slightly different standards when it comes to diamond grading. For example, a diamond that might receive an H color grade from a lab with the highest standards might receive a G grade from a different grading lab.

When you're diamond buying, pay special attention to clarity and cut grades.

• If you're opting for the lowest clarity grade we recommend, SI2, check the grading lab. If the lab is substandard, you might actually wind up with an I1 stone with major problems.
• For round diamonds, the cut grade is the most important factor. Although restricting your search to Excellent cuts should get you a great diamond, a stone with an Excellent grade issued by a substandard lab might actually have a poorer cut.

For these reasons, we recommend shopping only for diamonds graded by the Gemological Institute of America (GIA) or the American Gem Society (AGS), if possible. These labs have the highest grading standards, so you can be sure of your diamond's quality.

Polish and Symmetry

Some consumers think that a "Triple Ex" diamond, with Excellent cut, polish, and symmetry, will be superior to those with lower grades in polish and symmetry. However, polish and symmetry don't have as much of an impact on performance as you might think.

Slight imperfections can lower polish and symmetry grades, but these have little impact on the overall beauty or performance of the diamond. As long as you limit yourself to polish and symmetry grades of "Good" or better, you can find a quality diamond.

Also, keep in mind that a diamond's symmetry grade has nothing to do with the overall symmetry of its shape. Instead, it refers to facet symmetry. Not every great diamond will have perfect facet symmetry.

Fluorescence

Finally, fluorescence doesn't have a big effect on diamond quality. While fluorescent diamonds might show a slightly worse color under fluorescent lights than under sunlight, you're unlikely to ever notice it. Since the differences between adjacent color grades are so small, it's unlikely that fluorescence will ever make a difference. Fluorescence generally impacts color by less than one color grade.