Some people by gems by color or price, but for many, it may be better to buy gems by size - especially if you're in need to a gem to replace another previous item that was lost or damaged: Calibrated heart shaped facet cut gems and cabochon gems in 11 x 11 mm size. Buy a wide range of calibrated gemstones by size at wholesale from GemSelect.
As a general guideline, when it comes to 'calibrated' gems, they are not meant nor expected to be cut to exact measurements. For calibrated gemstones weighing under one carat, most jewelry settings will accommodate a gem which is within 0.2 mm of the calibrated size in order to fit a standard setting. For gemstones that weigh over one carat, a larger variance is acceptable, often around 0.3 mm or slightly higher even. This small variance can usually be accommodated for standard style settings. Round-cut gemstones should also have a greater variance in acceptable size when it comes to calibration; in fact it is usually possible to mount a round stone of any size in the closest standard setting.
I ordered my gems off this website called GemSelect, they have a good selection and it's easy to navigate. You can also have the gems professionally certified when you buy them, but they do provide certificates of their own.
Good experience with finding a variety of stones. Due to the vast selection, it is important to be able to search, and I had issues with the site not returning matches when I put in a specific size range. I was eventually able to narrow it down by sorting the items by size, but it was slower than if I could have typed it in. I also wish Gem Select would offer lab created stones (fully disclosed, of course!) so I could get some exotic colors more frequently. Overall, I love browsing and will continue to patronize, but this would put the site as my #1 go to.
I have been browsing stones on GemSelect for a few months. They have such a large selection and I found some stones I had never even hear of before visiting GemSelect! I cannot wait to receive my order and show my gems off!