1.3 Carat Trillion (8.44×8.44×3.38mm)

Depth percentage of Trillion cut is the ratio of the total depth (measured from table to culet) to its width. The total depth percentage of this diamond is 40%, which is OK.

Depth percentage for trillions is calculated with the following formula:

The face-up size of this 1.3 carat Trillion (8.44×8.44×3.38mm) is within the normal range for 1.3ct diamonds of this shape. Compared to 1.3ct Trillion reference diamond (see below), this diamond is of adequate size when viewed from the top. In short, all is OK, this diamond looks its weight.

The importance of face-up size

Diamonds are sold by weight (carats), but it's important to understand that weight doesn't equally translate into physical size, especially spread. Two diamonds of the same carat weight can vary greatly in spread, meaning that one diamond can appear larger than the other, even though they weight exactly the same.

Proper face-up size should play an important role when buying a diamond. When a diamond is set in a ring, your eyes will only see the face-up area, so you should make sure it's of adequate size. Adequate size also indicates a good cut, meaning better light performance. For example, if given a choice between a poorly cut 1.3 carat Trillion with less sparkle and the same face-up size as a well cut 1.2ct Trillion, which one would you choose?

Face-up area is a measure of the size of the diamond when viewed from above. It tells you how big the diamond is at the girdle plane. It's important for a diamond to have sufficient face-up size for its carat weight.

Face-up area per carat is calculated by dividing face-up area of the diamond with its carat weight. It tells you how many square millimeters of the top surface area a diamond is showing or would show for 1 carat weight. This can be useful when comparing stones of similar weights as it tells you how much spread per carat you will get.

Top surface area = 44.16 mm²
Weight = 1.3ct

Face-up area per carat = 44.16 ÷ 1.3 = 33.97mm²/ct

Trillions tend to show color a bit more in the corners, so it's recommended to stay relatively high on the color scale. The choice of color also depends on a setting:

	Solitaire	Small side-stones	Substantial side-stones
White gold/Platinum	H+	G+	same as side-stones+
Yellow gold	J+	I+	same as side-stones+
		e.g. pave setting	e.g. three-stone setting

Trillion cuts are quite good at masking inclusions. SI1 or SI2 clarity or higher is recommended.

Note: You can always go lower in clarity, but it's going to get increasingly difficult to find an eye-clean Trillion below the minimum recommended SI2 grade.

For best value, go with the lowest clarity possible that is still eye-clean. If a diamond is eye-clean, it doesn't matter, if it's flawless or SI2. It will look the same, provided all other characteristics are the same.

Professional and unbiased assessment of diamond characteristics is stated on a diamond grading report, commonly referred to as a certificate. Certificate, while not 100% reliable, is essential in determining a diamond's value.

The standard for diamond grading is pretty much set by GIA - Gemological Institute of America. They are the most reputable and consistent lab in the industry. AGS (American Gemological Society) is not far behind.

If a diamond is not certified by GIA or AGS, you can be pretty much certain that you are looking at lesser quality than indicated. This puts you in a bad position of not knowing the true diamond characteristics, which almost always results in overpaying. That is why a certificate from a well-respected grading lab is so important.

Blue fluorescence can have a positive, negative, or zero effect on a diamond. Diamonds in the lower color range (H or lower) can benefit from it, as it can make them look whiter, more colorless. On the other hand, strong fluorescence can cause a stone (especially in the higher color range D-G) to appear hazy or milky under certain light conditions. One of the biggest benefits of fluorescent diamonds is that they generally cost less.

GIA grades fluorescence as None, Faint, Medium, Strong, and Very Strong.

Faint fluorescence will have zero effect on color and overall appearance. Fluorescence of this type is not an issue and shouldn't be a purchasing factor.

Medium fluorescence will in most cases have zero to very small influence on color and overall appearance, however, colorless diamonds can sometimes exhibit negative effects and should be examined in different light conditions before purchasing.

Strong/Very Strong fluorescence requires caution. Generally, it's not a good idea to buy a colorless diamond with Strong/Very Strong fluorescence. As for lower color diamonds, even they can sometimes look hazy with strong fluorescence, so never buy a stone with this type of fluorescence without careful visual inspection.

The problem with diamond grading labs other than GIA or AGS is that they are looser and more inconsistent in their grading standards. A GIA color H is an IGI color G and an EGL/HRD color F. The same goes for clarity.

While it's true that IGI, EGL, and HRD diamonds are sold at a discount, you can be certain that the same stones would cost less, if they would be certified by GIA or AGS. Why? Because they would get lower grades and thus lower price. Lower than discounted IGI, EGL, and HRD stones with higher grades.

Diamond merchants use IGI, EGL, HRD, and alike to maximize their profits. They know they can sell diamonds with inflated grades for more, even if they're sold at a substantial discounts. Some merchants also use their in-house certification, usually for the sole purpose of increasing their profits. These kinds of certificates are meaningless.

Buying shy means choosing a diamond that falls just under the full-carat or half-carat mark. So instead of 1ct stone you go for 0.95ct; instead of 1.5ct you go for 1.4ct, and so on.

Because diamond prices jump dramatically at full-carat and half-carat weights, you can save a considerable amount of money when buying shy. Going up to 10% down in weight will result in a slight difference in size, but so slight it'll barely be noticed, if at all. To check this for yourself, use this site to compare different sizes.