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You Selected (40): Marquise Shape 18x9 mm Gems Clear All
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ID: 3865091 pcs
thumb image of 4.5ct Marquise Slice Bi-Color Ruby in Fuchsite (ID: 386509)
4.54ct Ruby in Fuchsite
18.72 x 9.02 x 2.65mm
USD 30.60
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ID: 3841481 pcs
thumb image of 6.9ct Marquise Cabochon Lavender Jadeite (ID: 384148)
6.90ct Jadeite
17.52 x 9.33 x 5.26mm
USD 48.30
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ID: 3524321 pcs
thumb image of 5.5ct Marquise Facet Violet Amethyst (ID: 352432)
5.48ct Amethyst
17.60 x 8.75 x 6.73mm
USD 38.36
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ID: 3872161 pcs
thumb image of 5.8ct Marquise Cabochon Lavender Jadeite (ID: 387216)
5.79ct Jadeite
17.87 x 9.03 x 3.90mm
USD 28.95
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ID: 3514181 pcs
thumb image of 5.1ct Marquise Facet Violet Amethyst (ID: 351418)
5.07ct Amethyst
17.95 x 8.75 x 5.93mm
USD 35.49
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ID: 3584151 pcs
thumb image of 6.8ct Marquise Facet Violet Amethyst (ID: 358415)
6.75ct Amethyst
18.26 x 9.05 x 7.51mm
USD 41.24
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ID: 3865051 pcs
thumb image of 4ct Marquise Slice Bi-Color Ruby in Fuchsite (ID: 386505)
3.95ct Ruby in Fuchsite
18.59 x 9.34 x 2.42mm
USD 26.62
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ID: 3513941 pcs
thumb image of 6.5ct Marquise Facet Violet Amethyst (ID: 351394)
6.53ct Amethyst
18.11 x 8.98 x 7.67mm
USD 45.71
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ID: 3866961 pcs
thumb image of 4.8ct Marquise Slice Bi-Color Ruby in Fuchsite (ID: 386696)
4.77ct Ruby in Fuchsite
18.63 x 8.88 x 2.82mm
USD 32.15
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ID: 3513541 pcs
thumb image of 5.7ct Marquise Facet Violet Amethyst (ID: 351354)
5.69ct Amethyst
18.14 x 8.75 x 6.54mm
USD 39.83
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ID: 3524821 pcs
thumb image of 6.6ct Marquise Facet Violet Amethyst (ID: 352482)
6.63ct Amethyst
18.35 x 9.28 x 7.53mm
USD 46.41
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ID: 3513521 pcs
thumb image of 6.8ct Marquise Facet Violet Amethyst (ID: 351352)
6.81ct Amethyst
18.09 x 9.24 x 7.30mm
USD 47.67
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ID: 3526711 pcs
thumb image of 5.2ct Marquise Facet Violet Amethyst (ID: 352671)
5.15ct Amethyst
17.64 x 9.02 x 6.28mm
USD 36.05
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ID: 3513891 pcs
thumb image of 5.8ct Marquise Facet Violet Amethyst (ID: 351389)
5.79ct Amethyst
17.82 x 8.83 x 6.25mm
USD 40.53
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ID: 3514061 pcs
thumb image of 5ct Marquise Facet Violet Amethyst (ID: 351406)
4.95ct Amethyst
18.05 x 8.89 x 5.61mm
USD 34.65
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ID: 3514091 pcs
thumb image of 6.4ct Marquise Facet Violet Amethyst (ID: 351409)
6.44ct Amethyst
17.80 x 9.34 x 6.84mm
USD 45.08
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ID: 3586731 pcs
thumb image of 6.6ct Marquise Facet Violet Amethyst (ID: 358673)
6.61ct Amethyst
18.34 x 9.28 x 7.39mm
USD 40.32
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ID: 3586761 pcs
thumb image of 6.3ct Marquise Facet Violet Amethyst (ID: 358676)
6.29ct Amethyst
18.14 x 9.29 x 7.02mm
USD 38.37
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ID: 3585101 pcs
thumb image of 7.1ct Marquise Facet Violet Amethyst (ID: 358510)
7.11ct Amethyst
18.32 x 9.21 x 7.77mm
USD 43.44
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ID: 3514151 pcs
thumb image of 7.6ct Marquise Facet Violet Amethyst (ID: 351415)
7.56ct Amethyst
18.20 x 9.34 x 8.16mm
USD 52.92
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ID: 3865061 pcs
thumb image of 3.9ct Marquise Slice Bi-Color Ruby in Fuchsite (ID: 386506)
3.90ct Ruby in Fuchsite
17.86 x 9.32 x 2.46mm
USD 26.29
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Marquise Shape 18x9 mm Gems
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.

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Size and Weight

Gems are always measured in Millimeter (mm)

Dimensions are given as;
length x width x depth,
except for round stones which are;
diameter x depth

Select gems by size, not by weight!
Gem varieties vary in density, so carat weight is not a good indication of size

Note: 1ct = 0.2g

Size Comparison Chart