Some people by gems by color or price, but for many, it is best to buy gems by shape and size - especially if you're in need of a gem to replace a previous item that was lost or damaged. Calibrated marquise shaped facet cut gems, gemstone carvings and cabochons available in 18 mm x 9 mm sizes. For the largest selection of colored gemstones, Shop GemSelect Online.
As a general guideline, when it comes to calibrated gems, they are not usually expected to be cut to exact measurements and specifications. But rather, they're cut with slight variance in size, though the close approximatation in size is not clearly defined, there are general guidelines for what is considered acceptable. Obviously larger and heavy carat weight stones allow more room in size for variance, while smaller stones may leave little to none. This means a large 30mm calibrated gemstone, could actually be closer to 31 millimeters. For this reason, we recommend to always view the exact size in addition to the calibrated size details. The exact size will inform you of the variance you can expect. Some setting styles are more flexible with variance, such as prong settings, while other styles of mountings may need almost an exact size to the fraction of millimeter.
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 round shape settings will allow 0.3 mm or slightly higher even. This small variance can usually be accommodated for most 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.
