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Gemtype Color Shape Weight Size Date Clarity Price Origin
You Selected (15): Octagon Shape 18x13 mm Gems Clear All
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ID: 4166271 pcs
16.53ct Smoky Quartz
18.07 x 13.05 x 9.02mm
USD 24.80
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ID: 3840101 pcs
20.43ct Apatite
17.46 x 13.17 x 10.35mm
USD 1090.55
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ID: 3992911 pcs
17.77ct Quartz
18.36 x 12.87 x 10.00mm
USD 28.25
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ID: 4166341 pcs
15.82ct Smoky Quartz
17.96 x 12.95 x 8.96mm
USD 23.73
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ID: 4020371 pcs
14.09ct Rutile Quartz
18.14 x 13.16 x 9.17mm
USD 37.62
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ID: 4090071 pcs
18.00ct Topaz
17.71 x 12.98 x 8.59mm
USD 120.60
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ID: 3989751 pcs
16.17ct Quartz
17.72 x 13.28 x 9.17mm
USD 25.71
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ID: 4166291 pcs
15.62ct Smoky Quartz
18.05 x 13.07 x 8.81mm
USD 23.43
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ID: 4090051 pcs
18.84ct Topaz
17.92 x 13.01 x 8.84mm
USD 126.23
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ID: 4166301 pcs
17.24ct Smoky Quartz
18.03 x 13.11 x 9.36mm
USD 25.86
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ID: 3945091 pcs
15.15ct Ametrine
18.55 x 12.89 x 8.35mm
USD 80.75
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ID: 4226541 pcs
17.91ct Topaz
17.98 x 13.03 x 8.41mm
USD 113.19
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ID: 4093771 pcs
19.64ct Topaz
17.92 x 12.88 x 8.73mm
USD 131.59
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ID: 4166281 pcs
16.81ct Smoky Quartz
18.03 x 13.09 x 8.99mm
USD 25.21
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ID: 4093951 pcs
19.02ct Topaz
17.91 x 12.90 x 8.65mm
USD 127.43
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Octagon Shape 18x13 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 Octagon shape / Emerald-Cut, faceted and cabochon gems available now in 18 x 13 mm size range. Shop a wide range of calibrated gemstones by size online at wholesale from GemSelect.

As a general guideline, when it comes to 'calibrated' gems, they are not usually 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 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