Heart Shaped Diamond Symmetry Guide: How to Judge Lobes, Cleft and Point

What is heart shaped diamond symmetry?

Symmetry, in a diamond, means how precisely one part of the stone mirrors another. In a round brilliant there are many mirror lines. In a heart there is only one: an imaginary vertical line that runs from the centre of the cleft (the dip between the two lobes) straight down through the point. Everything to the left of that line should be a reflection of everything to the right.

That single line is why the heart is so unforgiving. With only one axis to compare against, your eye picks up small differences very quickly, especially at the top of the stone where the two lobes sit side by side. If you are new to the shape itself, start with our complete heart shaped diamond guide, which covers ratio, size, colour and settings. This page goes deeper on one thing: how to tell a well-balanced heart from one that is slightly off.

When gemmologists talk about heart symmetry, they are looking at six areas: the two lobes (the rounded tops), the cleft, the shoulders (where each lobe turns down into the side), the wings (the long curved sides), the belly (the widest part across the middle) and the point. Any of these can be uneven, and some faults matter far more than others. If a term is unfamiliar, the GemTrove jewellery glossary explains it in plain English.

The heart sits within the elongated and fancy brilliant family of cuts, alongside the pear, oval and marquise. All of them are judged partly on outline, but the heart's two lobes and cleft give it more parts that have to match than any of its relatives.

Outline, facet and optical symmetry: what is the difference?

People use the word symmetry for three different things, and a heart can be strong on one and weak on another. Knowing which is which stops you relying on the wrong number.

The symmetry grade on a report is a measure of facet symmetry. A grader looks at things like an off-centre table (the large flat top facet), an off-centre culet (the tiny facet or point at the bottom), crown and pavilion facets that do not line up, a wavy girdle (the thin edge around the stone) and extra facets. Our page on how the Excellent to Poor symmetry grades work covers each of these in detail.

Outline symmetry is a judgement of shape appeal. Grading labs do take obvious outline problems into account to some degree, but the grade is not a full verdict on whether the outline looks balanced. And optical symmetry, the even spread of light, is a separate idea again; see the difference between facet symmetry and optical symmetry for why the two do not always agree.

What do symmetry grades mean for a heart shaped diamond?

Major labs such as GIA and IGI grade symmetry on a five-step scale. For heart shapes (and other fancy shapes), GIA does not give an overall cut grade the way it does for round brilliants, so the polish and symmetry grades are the only cut-related grades you get on the report. That makes the symmetry grade more important for a heart than for a round.

Most people choosing an excellent symmetry heart diamond, or one graded Very Good, find the two indistinguishable in a ring. The step down to Good is where it pays to look harder. Some Good-symmetry hearts are lovely because the issue is a slightly misaligned facet deep in the pavilion (the lower half of the stone) that you will never notice. Others have an off-centre table that pulls the whole pattern to one side.

Natural hearts graded by GIA and lab-grown hearts graded by IGI both show a symmetry grade, and the scale reads the same way. A laboratory-grown diamond is real diamond, so the same symmetry checks apply to it in exactly the same way.

What are the common symmetry faults in heart shaped diamonds?

These are the faults gemmologists look for, roughly in order of how much they change what you see on the hand.

The cleft deserves extra attention. A crisp, clearly defined cleft is what separates a heart from a pear, and our guide to how a heart differs from a pear shows how quickly a shallow cleft blurs the two. At the other end, a very deep cleft looks dramatic but creates a second thin, exposed area alongside the point, which the setting needs to cover.

In a 1 carat heart (roughly 6.8 mm wide), the lobes are only a few millimetres across, so a height difference of a fraction of a millimetre can already be visible. That is why photos and video taken straight-on, not at an angle, are essential when you compare stones.

How does the ratio affect how symmetrical a heart looks?

The length-to-width ratio is the stone's length (top of the lobes to the point) divided by its width (across the lobes). It is not a symmetry measure as such, but it changes how easy it is to spot asymmetry.

• Below about 0.90: a wide, squat heart. The lobes flatten and the wings get short, so an uneven lobe is very obvious against the broad top.
• About 0.90–1.10: the classic balanced heart. Lobes, wings and point are in proportion, and small faults are easiest to judge fairly.
• Above about 1.10: a slim, longer heart. The point becomes long and narrow, so a crooked point stands out more.

Size plays a part too. Under about half a carat, the lobes and cleft become so small that the outline can read as a rounded triangle no matter how well it is cut, and claws cover a larger share of the edge. Our page on the minimum size for a heart to read clearly explains why most people choose 0.50 carat or more.

One trap: two hearts can have identical length and width measurements, and therefore identical ratios, while one has matched lobes and the other does not. The ratio tells you the box the heart fits in, not whether it is balanced inside that box. Always look at the outline itself. Depth matters as well: a deep heart carries weight underneath and faces up smaller, which our comparison of which shapes face up largest for their weight puts into numbers.

Does the bow-tie show symmetry problems in a heart diamond?

Many hearts show a bow-tie: a darker band across the belly where light leaks out of the pavilion instead of returning to your eye. A faint bow-tie that shifts as the stone moves is normal and adds contrast. What matters for symmetry is whether the bow-tie is even.

If the dark area is heavier on one side, or sits off-centre, it often points to uneven pavilion angles or an off-centre culet, which is a facet symmetry problem. It can also make a heart with a perfect outline look as if it leans. This is optical symmetry at work, the idea covered in the section on the three kinds of symmetry above, and reflector images or video are the clearest way to reveal it.

• Even, faint bow-tie that comes and goes: normal and fine.
• Dark band fixed in every position: a proportion problem, whether symmetrical or not.
• Dark patch on one half only: a sign the two halves are cut differently; check the symmetry grade and the table position.

Bow-ties are rarely visible in still photos. A 360° video, watched while you keep your eye on the belly, is the most reliable way to judge it before you see the stone in person.

How does heart symmetry compare with pear and marquise symmetry?

The heart, pear and marquise are all judged on symmetry along their length, but the heart has more parts that must match.

Because a pear has a rounded head instead of two lobes and a cleft, it is a little more forgiving at the top. Our guide to checking symmetry in a pear diamond uses the same fold test, and the pear cut diamond guide covers the shape more broadly. A marquise is the opposite: it has two mirror lines, so both ends must line up with each other as well as left with right; see the marquise symmetry checks for how that works, and our marquise cut overview for ratio and setting advice.

All three belong to the fancy-shape family. For a wider view of how every cut is built and judged, start with our overview of every diamond shape.

Can a setting hide a heart's symmetry faults?

A setting can soften small faults, but it cannot fix a badly mismatched heart. It helps to know what each style does to the outline.

• Three claws with a V-claw at the point: the V-claw wraps the point and can disguise a tip that is very slightly off-line. Claws at each lobe can visually even out small differences in lobe height.
• Five claws: adds a claw either side of the cleft, which frames the cleft and can make a slightly off-centre one less obvious.
• Bezel or half-bezel: a rim of metal follows the whole outline. It is very secure but traces every curve, so uneven wings can become more noticeable.
• Halo: a ring of small diamonds makes the heart look larger, but it follows the shape closely and can exaggerate an uneven outline if the halo is made to match.

The safer path is to choose a well-balanced stone first, then design around it. For side-by-side examples, see the V-claw, bezel and halo settings that protect a heart and how each one frames the lobes. A balanced heart also makes it easier to pair a band; our guide to wedding bands that sit flush beside a heart shows contoured and straight options.

When a ring is designed in CAD (computer-aided design), the claws can be placed to suit the actual measured stone, not a generic heart template. That matters for a heart, because a claw positioned even slightly off the lobe can make an otherwise balanced stone look uneven.

Does symmetry change the price of a heart shaped diamond?

Yes, but usually less than you might expect. The symmetry grade itself tends to move the price only modestly between Excellent, Very Good and Good, while carat, colour and clarity move it far more. What pushes the price of a heart up within the same grades is shape appeal: a heart with matched lobes, a crisp centred cleft and a straight point is in more demand than one with the same report but a weaker outline. Our page on how prices differ between diamond shapes sets hearts against the other main cuts.

Hearts are cut from both natural and laboratory-grown diamond. The two look identical, have the same hardness (10 on the Mohs scale) and refractive index (about 2.42), and are judged on symmetry in exactly the same way. Lab-grown hearts cost much less, which often means you can be more selective about symmetry within the same budget. Natural hearts are rarer, so a truly well-matched one can take longer to find.

These are broad ranges only and move with the market. Whichever you choose, ask for the grading report, a face-up photo taken straight-on and a 360° video, so you can check symmetry yourself rather than relying on the grade alone.

How do you check heart shaped diamond symmetry? Step by step

1. Read the report. Note the symmetry and polish grades, the measurements and whether the diamond is natural or lab-grown. Shortlist Very Good or Excellent symmetry, and look closely at any Good.
2. Work out the ratio. Divide length by width; about 0.90–1.10 is where symmetry is easiest to judge fairly.
3. Get a straight-on face-up image. Angled photos distort the lobes. Ask for one taken directly above, point down.
4. Do the fold test. Picture a line from the centre of the cleft to the point. Compare lobe height, lobe width, shoulders and wings on each side.
5. Check the cleft and point. The cleft should be crisp and centred; the point should sit directly below it, not to one side.
6. Watch the 360° video. Look for an even bow-tie and a sparkle pattern that matches on both halves as the stone turns.
7. Check the table and culet. In the face-up view, the table should sit centred on the mirror line, with the culet below it.
8. Plan the setting around the stone. Confirm the claws or bezel will be placed to suit the measured outline and protect the point.

If a heart passes all eight checks, its symmetry grade and its look on the hand will agree. If it only passes on paper, trust your eye: the outline is what you will see every day.