JA is a good source, but don’t rely on their customer service to choose a diamond. They suck at it. Once you have selected a few diamonds in your budget and meet the below criteria, post your budget and potential stones over on Pricescope/RockyTalky. They will help you find a stunning stone for your selected setting.
Round Diamond 101 from PS and my own experience.
Summary — Within the cut parameters below, HCA below 2, “eye-clean”, G/H (modern round) down to I/J (super-ideal), certified by GIA, AGS or HRD only.
Cut: This is the most important element of making a diamond sparkle. The actual way the facets are cut and interact is what makes a stone shine or not. Only accept “Excellent” or “Ideal” on the certification. The cut grade provides a single rating that weighs the combined impact of facet shapes and angles, girdle width, culet size, polish, and symmetry. But, it is subjective to a point.
These measurements stay in ideal-cut territory of a GIA excellent cut round stone. They should be on the website for round or on the certification.
- table: 54-58
- depth: 59-62.3
- crown angle: 33.5-35.0*
- pavilion angle: 40.6-40.9 (sometimes 41.0)*
*And the crown and pavilion angles must be complementary which is what the HCA checks for you.
If a stone fits those numbers, then run it through the HCA tool. This is an exclusion tool, but it will eliminate any round that will be an automatic no. http://www.pricescope.com/tools/hca; You want to see Excellent on light return, fire, and scintillation, and very good on spread. An overall score of 2.0 or lower means a diamond is worth exploring further (but a 1.0 isn’t necessarily better than 1.9).
Clarity: You want an ‘eye clean’ stone as stated by a gemologist if you are looking at a SI1, SI2. VS2 is ‘safe’ if a gemologist is not involved.
Color: This is personal, but if you set the J in yellow or rose gold, the body color should be minimally visible. Setting it in white gold/platinum (or with a halo of higher color diamonds) will offer your eye a visible contrast and can make the body color more obvious. I personally stick with G/H in modern rounds for platinum/white gold. The only J I would place in platinum would be one of a few super-ideal branded diamonds (e.g., High Performance Diamonds, BrianGavin Blue, etc.).
Flourescense: None, fair or medium. Avoid strong fluorescence in D,E,F or VeryStrong on G or H. Fluorescence is a cool effect in diamonds, but can contribute to haziness.
Certification: GIA, HRD, AGS are the best. EGL, IGS and most others are very soft. Assume you are looking at a color 2 lower and clarity 1 lower (at least) for non-GIS/HRD/AGS when compared to a GIA stone.