Help! I think my girlfriend wants a Marquise Diamond

Question: Hi, Diamond Buying Advice,

I've been looking to get an engagement ring, but am not really sure about all the different diamonds. I have it on good authority that my girlfriend likes the Marquise diamond. Where can I buy the Marquise? Is it expensive?

R.R.

Answer: Hello RR,

The marquise shape of diamond is a very elegant shape. It is often chosen to be worn by women with slender fingers. This shape falls under the category of "fancy cut". 

The length to width ratio is quite important when looking at marquise cut diamonds. I always recommend buying a diamond with an "Excellent" cut. The key to getting a marquise diamond which is brilliant and real sparkly is to check that the following are true of the diamond.

It should have a

Color "I" or lighter

Length to width ratio of 1.80 : 1.00.

As well as a depth of 61%.

One or two percentage points variation on the depth will make almost no difference. But these proportions mentioned above will give you the most brilliance.

The number for the depth percentage is found on a diamond's grading report as well as within the search parameters on a diamond vendor's website.

The length to width ratio is not written on a grading report.

This is the way you calculate it.

Let's say you look at a marquise diamond's grading report which says:

Measurements: 10.25 x 5.75 x 3.47 mm

Press the calculator button on your keyboard (if there is one)

Type in: 

10.75 
/
5.75

= 1.782608695652174

This gives is the length to width ratio.

1.78 : 1.00

This very close to the ideal proportions, but we can look further as it's possible to find one that has proportions even closer to 1.80 : 1.00. 

Here is another one: 10.38 x 5.66 x 3.49 mm

This one gives us a length to width ratio of 

1.83 : 1.00

This one we see ends up being slightly over our ideal, so we continue our search. the next one we decide to check out is a slightly smaller stone with the measurements of 9.69 x 4.70 x 2.76 mm

We do the math: 

9.69 
/
4.70

We find that this one is actually no closer to our ideal as it has a length to width ratio of

2.06 : 1.00

It looks like the first diamond of the three we looked at was the best choice and we might go with that one.

As far as price goes, marquise diamonds are often priced considerably lower than round brilliant diamonds with the same specifications. See these two diamonds compared. The one that is slightly larger is the marquise, and yet it is considerably less expensive than the round diamond. Not everything is exactly the same, however they are both quite close to being near the top of the range with identical color and clarity. 

CARAT	COLOR	CLARITY	CUT	DEPTH	TABLE	POLISH	SYM.	SHAPE	PRICE
0.95	I	VVS2	IDEAL	62.2%	58	EX	EX	ROUND	$6,301
0.98	I	VVS2	PREM	65.4%	63	VG	GD	MARQUISE	$3,719

See these recommended diamond vendors websites for up to date prices.