Your best bet is finding a reputable jeweler, not mall jewelers like Kay, Jared, etc. Those places have a reputation for subpar quality, over-estimating diamond grading, etc. and should be avoided all together. Even Blue Nile and James Allen are now owned by the parent company of many of those mall jewelers, so they aren’t as reputable as they once were. Since diamond melee/diamonds under .25ct are generally not sent to GIA (the most reputable independent lab) for grading, you are relying on the jewelers “estimation” of grading. Some jewelers provide in-house appraisals and/or certificates from in-house gemologists (sometimes “GIA trained”); however, being in-house there is an obvious conflict and that documentation isn’t really reliable. Costco has a surprisingly good reputation for quality diamond jewelry and a great return policy. Also check out ID Jewelry in NYC or online. Whiteflash and Brian Gavin are other reputable sources. GL