There are subtle variations to these values. (If you know your gemstone density values well, you can estimate the weight of a standard size gem by sight). The opal, with an SG of 2.15, will only weigh 0.61 carats. The sapphire, with an SG of 4, will weigh 1.14 carats. The diamond, with an SG of 3.52, will weigh 1 carat. For example, a 6.5 mm round diamond, sapphire, and opal, all cut in the same proportions, will all weigh different. The density or specific gravity (SG) of the material will also affect the weight. Thus, they’ll weigh more than the sizes on the chart. Typically, gem cutters cut colored gemstones with greater volume than diamonds.

The carat weights given for standard gem sizes in the following chart apply to diamonds cut to ideal proportions. Over one carat, a 0.2 mm variance can usually be accommodated, sometimes more. As a general rule, gems under one carat can fall within 0.1 mm of the setting size. For other shapes, metalsmiths must consider a variety of factors. For example, any round gem can be put in a standard setting. A skilled metalsmith can modify a standard setting to accommodate a variety of gem sizes. No, a gem doesn’t need to be the precise size of the jewelry setting. Do Gems Need to Match Standard Settings Precisely? However, in other circumstances, the gem’s value doesn’t justify the cost of a custom setting. You can then pay for a custom setting later. Under some circumstances, the stone’s value makes cutting for maximum yield worthwhile. Choosing a Standard Setting or a Custom Setting Emerald-cut tourmaline, 4.52 cts, slight color shift. It has a range of standard gem sizes for mass-produced jewelry settings. Although named after the emerald, which often receives this rectangular cut with trimmed corners, the popular emerald cut design can be applied to many gemstones.

Average cost for 5 ct amethyst gemstone