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Gemtype Color Shape Weight Size Date Clarity Price Origin
You Selected (7): Octagon Shape 18x13 mm Gems Clear All
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ID: 4166291 pcs
thumb image of 15.6ct Octagon Facet Brown Smoky Quartz (ID: 416629)
15.62 ct Smoky Quartz
18.1 x 13.1 mm
$ 23.43
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ID: 4166341 pcs
thumb image of 15.8ct Octagon Facet Brown Smoky Quartz (ID: 416634)
15.82 ct Smoky Quartz
18 x 13 mm
$ 23.73
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ID: 4166301 pcs
thumb image of 17.2ct Octagon Facet Brown Smoky Quartz (ID: 416630)
17.24 ct Smoky Quartz
18 x 13.1 mm
$ 25.86
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ID: 4020371 pcs
thumb image of 14.1ct Octagon Facet Colorless Golden Rutile Quartz (ID: 402037)
14.09 ct Rutile Quartz
18.1 x 13.2 mm
$ 37.62
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ID: 4090071 pcs
thumb image of 18ct Octagon Facet Swiss Blue Topaz (ID: 409007)
18.00 ct Topaz
17.7 x 13 mm
$ 120.60
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ID: 4166271 pcs
thumb image of 16.5ct Octagon Facet Brown Smoky Quartz (ID: 416627)
16.53 ct Smoky Quartz
18.1 x 13.1 mm
$ 24.80
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ID: 3989751 pcs
thumb image of 16.2ct Octagon / Scissor Cut Lemon Quartz (ID: 398975)
16.17 ct Quartz
17.7 x 13.3 mm
$ 25.71
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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