The Australian Lab Grown Diamond Buying Guide

Buying a lab grown diamond well comes down to knowing which specifications to protect and which to let go, and the answer is different for every shape. A round brilliant hides colour and inclusions. An emerald cut hides nothing. Buy them the same way and you will overpay on one and underbuy on the other.

This guide runs in the order a real buyer makes the decisions: shape, then budget, then which of the 4Cs matter for that shape, then setting, then metal. At the end there is a checklist you can take to any jeweller, including ones that are not us.

Decision one: shape

Shape comes first, because it is a taste decision and because it constrains everything after it. There is no correct shape and none that is better value in the abstract. There is only the shape your partner wants to look at for the next fifty years.

What shape determines: which grades you need to protect, how large the stone looks per carat, which settings work, and which wedding bands will sit flush against it later.

Two broad families. Brilliant cuts (round, oval, cushion, pear, marquise, radiant, princess) are faceted to scatter light into many small flashes, and that scatter conceals slight body colour and small inclusions. Step cuts (emerald, asscher, baguette) are faceted in long parallel planes like a staircase, producing broad flashes and an open, glassy look. Step cuts conceal almost nothing.

That single distinction drives most of the advice below.

Decision two: budget

Set the number before you look at stones, not after, because grades ratchet upward when you shop without a ceiling.

Lab grown pricing gives you a choice mined pricing does not: at any given budget you can have size, or you can have top grades, and you can afford considerably more of both than you could five years ago, because lab grown prices have fallen substantially since 2020 as production scaled. Our lab grown diamond designs start at AU$1,350, and moissanite starts at AU$800.

My order of spending, and I will defend it anywhere:

1. Cut quality. It is the only thing visible from across a room.
2. The setting. The setting is what fails, not the stone.
3. Carat.
4. Colour and clarity, down to the floors set out below.

Most people invert two and four, and end up with a beautifully graded stone in a setting that loosens inside five years.

Decision three: which of the 4Cs to protect, by shape

This is the core of the guide. The floors below are where I would stop dropping a grade, not targets to aim at.

Shape	Cut and finish	Colour floor	Clarity floor	Notes
Round brilliant	Excellent cut grade, non negotiable	G or H	VS2 or SI1	The most forgiving shape. Scatter hides both colour and inclusions. Spend everything on cut
Oval	Excellent polish and symmetry	G or H	VS2 or SI1	Forgiving on colour and clarity. Check for a bow tie. Looks larger per carat than round
Cushion	Very Good to Excellent finish	G or H	VS2 or SI1	Forgiving. Softer facets, hides small inclusions well
Radiant	Excellent finish	G or H	VS2	Brilliant faceting inside a rectangular outline. Forgiving, and looks larger per carat
Princess	Excellent finish, check corners	G or H	VS2	Corners are vulnerable. Protect them in the setting
Pear	Excellent symmetry is essential	G or H	VS2	Poor symmetry makes the point look bent. Check the point sits in line with the centre of the base
Marquise	Excellent symmetry is essential	G or H	VS2	Two points, both must line up. Highest looking size per carat of any shape
Emerald	Excellent polish, open table shows everything	F or G	VS1	Step cut. Clarity and colour both matter more. Save on carat instead
Asscher	Excellent polish and symmetry	F or G	VS1	Same rules as emerald. Square outline shows the pavilion clearly

Two things to take from the table.

Round, oval and cushion are where the savings are. Their faceting is busy enough that G or H colour reads as white face up in a setting, and a well placed SI1 inclusion is invisible without a loupe. Drop both, keep an excellent cut, put the difference into size or the setting.

Emerald and asscher are the opposite trade. The long open facets act like windows into the stone. Body colour pools visibly and inclusions sit exposed in the middle of the table with nothing to break them up. Hold colour at F or G and clarity at VS1, and buy a smaller stone to pay for it. A one carat emerald in VS1 looks considerably better than a 1.5 carat in SI1, and it is the shape where I most often talk people down in size.

On pear and marquise: many fancy shapes receive no overall cut grade at all, so polish and symmetry are the only proxies you have. Good is not good enough on a pointed shape. A fractionally off centre point is visible from normal distance and cannot be fixed later.

On the clarity plot: look at where the inclusions sit, not just the grade. An SI1 with a crystal near the girdle that will disappear under a claw beats a VS2 with a feather in the middle of the table. If you have not read a grading report before, what an IGI certificate tells you walks through every field, including how to verify the report number on IGI's own site.

Length to width ratios

Ratio is length divided by width, and it is where taste becomes a number you can shop by. Wider looks rounder and softer. Longer looks more dramatic. Neither is correct, but there are ranges outside which most people think something looks wrong.

• Oval: 1.30 to 1.50, with most people landing at 1.35 to 1.45. Below 1.30 it reads as a slightly failed round. Above 1.55 it gets noticeably narrow.
• Pear: 1.45 to 1.75. Around 1.50 to 1.60 is the classic teardrop. Longer reads more elegant and more fragile at the point.
• Emerald: 1.30 to 1.50 for the classic rectangle, with 1.40 the standard. Below 1.20 it approaches square and reads as an asscher.
• Marquise: 1.85 to 2.10, with 1.90 to 2.00 traditional. Below 1.80 it looks stubby.
• Radiant: 1.00 to 1.05 for square, or 1.20 to 1.50 for elongated. Decide which you want before you shop, because they look like different shapes.

Ask for the measurements, not just the ratio, and divide length by width yourself. They are on every report.

One practical point on size: elongated shapes look larger per carat than round, because they spread more weight across the top of the stone rather than down into the depth. A 1.00ct oval or marquise reads as visibly bigger on a hand than a 1.00ct round. If size on the finger matters more than the number on the paperwork, that is free size.

The bow tie

Elongated brilliant cuts, ovals and pears and marquises in particular, can show a dark band across the centre shaped like a bow tie. It is caused by the pavilion facets shadowing light out of that zone, and it is a function of how the stone was cut. Almost every oval has some. The question is how much.

A faint bow tie that only appears at certain angles is normal and nobody notices it. A strong one that sits there as a solid grey band in every light is a defect you will see every day and never unsee.

How to check for it:

1. Look at the stone face up in ordinary indoor light, not under a jeweller's spotlight. Spotlights blast light back into the stone and hide it.
2. Rock it slowly back and forth and watch the centre.
3. Ask for video of the actual stone, face up, moving, in normal light. Not a stock image of the shape, and not a still photograph.
4. Ignore the certificate here. Bow tie is not graded and appears on no report. This is an eyes only assessment.

If you are buying online from a stock list and cannot get moving video of the specific stone, do not buy an oval, pear or marquise. Buy a round.

Decision four: setting

The setting is the part that fails. Stones do not wear out. Claws do.

Solitaire. Six claws hold more securely and cover slightly more of the stone. Four claws show more of it and look cleaner. Both are fine when made properly.

Halo. A ring of small stones around the centre, making a smaller centre read as considerably larger. Honest downside: more small stones means more small settings, and small settings are what loosen.

Bezel. Metal wrapping the girdle. The most secure option by a distance, and the right answer for anyone who works with their hands. It covers a little of the stone and slightly reduces light entry from the sides.

Three stone, pavé and eternity bands. More stones, more settings, more to keep an eye on. Full eternity bands generally cannot be resized at all, which is a serious consideration for a ring you will own for decades.

What to ask about, regardless of style:

• Shank thickness at the base. Under about 1.8mm on a ring worn daily by someone active and it will wear thin and eventually crack. This is the most common repair I see.
• Claw thickness and finish. Thin, unfinished claws are the second most common failure.
• Setting height. A high set stone catches on things. A low set one is more secure and needs the wedding band shaped to fit.
• Whether the design can be resized. Ask before, not after.

Shape and setting interact. A pear needs a V shaped claw over the point. A princess needs its corners covered. An emerald cut wants claws that suit its corners rather than fighting them.

Decision five: metal

All three of the usual options are legitimate. They fail differently, and nobody tells you that at the counter.

White gold. Gold alloyed white and then plated with rhodium for the bright white finish. That plating wears, fastest on the underside of the band where it rubs, and needs redoing periodically to keep the colour. A recurring cost and a trip to a jeweller, forever. Not a fault, just maintenance nobody mentions at the counter.

Platinum. Denser, more expensive per gram, and needs no plating because it is white all the way through. It does not stay glossy. It scratches into a soft grey patina, which some people love and others are dismayed by. Platinum displaces rather than loses metal when scratched, so it wears gracefully across decades. If you want white and do not want ongoing plating, this is the answer.

Yellow and rose gold. The most forgiving of daily wear by a wide margin. No plating, and scratches disappear into the colour rather than showing as bright marks. Rose gold takes its colour from copper, which makes the alloy slightly harder. For someone who works with their hands, yellow or rose gold in 14ct is the practical answer.

On karat: 18ct is richer in colour, 14ct is harder and resists bending better. For a ring worn every day by an active person, 14ct is more durable, and I say that as someone who could just as easily sell you the more expensive option.

The checklist

Take this to any jeweller. If they can answer all of it comfortably, they know what they are doing.

About the stone

1. Can I have the report number now, so I can check it on the laboratory's site myself?
2. What are the exact measurements in millimetres, and what is the length to width ratio?
3. What is the cut grade, and if the shape has no cut grade, what are the polish and symmetry?
4. Where are the inclusions on the plot, and will any of them sit under a claw?
5. Can I see video of this exact stone, face up, moving, in normal indoor light?
6. Is there a bow tie, and how strong is it?
7. Is the girdle laser inscribed, and can you show me the inscription under magnification?

About the setting

1. How thick is the shank at the base, in millimetres?
2. What holds the stone, and how are the claws finished?
3. Can this design be resized, and how many times?
4. Is the ring cast or hand made, and who made it?

About what happens next

1. What does the warranty cover, and for how long?
2. What does a resize cost, now and in twenty years?
3. Who repairs it if a claw moves, and where does the ring go?
4. Do you provide a valuation for insurance?

That last group is the one people skip and the one that matters most across a lifetime of wear. Ours: a lifetime warranty on craftsmanship and on the optical properties of the stone, and one free resize within three months of purchase, with additional resizes from $80.

Our designs begin at AU$1,350 in the lab grown diamond engagement rings collection, and the moissanite engagement rings collection covers the same shapes and settings from AU$800. We send a free ring sizer before anything is cast, and you can book an appointment at the Southbank studio or a design consultation by video call.

Common questions

What colour grade should I buy in a lab grown diamond?

G or H for round, oval, cushion, radiant, princess, pear and marquise. F or G for emerald and asscher, because step cuts show body colour far more readily. Below H you start to see warmth face up, particularly in white metal.

What clarity is eye clean?

VS2 and most SI1 stones are eye clean in brilliant cuts, but it depends on where the inclusion sits, not only the grade. In emerald and asscher cuts, hold at VS1. Always look at the plot rather than the grade alone.

Which diamond shape looks biggest for the carat weight?

Marquise, then oval and pear, then emerald and radiant. Elongated shapes spread more weight across the top of the stone. Round brilliants carry more weight in depth, so they look smallest per carat.

Is a bow tie a defect?

A faint one is normal in oval, pear and marquise and is not a problem. A strong dark band across the centre in ordinary light is a cutting fault you will see every day. It never appears on a grading report, so you have to check it yourself with video.

Should I choose platinum or white gold?

Platinum if you do not want to re plate the ring periodically and you are comfortable with it developing a soft patina. White gold if you want the bright white finish and are willing to have the rhodium redone as it wears. Cost aside, that is the real difference.

Is 14ct or 18ct better for an engagement ring?

18ct has richer colour and higher gold content. 14ct is harder and holds its shape better under daily wear. For someone active or working with their hands, 14ct is the more practical choice.