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Gemtype Color Shape Weight Size Clarity Price Origin
You Selected (574): Round Shape 12 mm Gems Clear All
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9.6ct Round Facet Pinkish Rose Malaya Garnet Gem (ID: 498583)
9.59 ct Malaya Garnet
12.5 mm
$ 383.60
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5.2ct Round Facet Red Strawberry Quartz Gem (ID: 474908)
5.24 ct Strawberry Quartz
11.9 mm
$ 36.68
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2 pcs
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12.8ct Drilled Sphere Gold Brown Tiger's Eye Gem (ID: 422964)
12.84 ct (total 25.67ctw) Tiger's Eye
11.6 mm
$ 20.54
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5.4ct Round Facet Yellow Golden Citrine Gem (ID: 338817)
5.44 ct Citrine
11.7 mm
$ 43.52
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4.7ct Round Facet Brown Smoky Quartz Gem (ID: 503804)
4.71 ct Smoky Quartz
11.7 mm
$ 14.13
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7.2ct Round Cabochon Green Maw-Sit-Sit Gem (ID: 477809)
7.20 ct Maw-Sit-Sit
11.9 mm
$ 15.34
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4.7ct Round Facet Brown Smoky Quartz Gem (ID: 464005)
4.70 ct Smoky Quartz
11.6 mm
$ 7.05
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2 pcs
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7.1ct Round Rose-Cut Black Spinel Gem (ID: 438377)
7.14 ct (total 14.27ctw) Spinel
12 mm
$ 42.81
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12.8ct Drilled Sphere Multicolor Jasper Gem (ID: 361818)
12.80 ct (total 25.59ctw) Jasper
12.4 mm
$ 25.59
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6.2ct Round Cabochon Green Jadeite Gem (ID: 470587)
6.18 ct (total 12.36ctw) Jadeite
11.7 mm
$ 37.08
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7.2ct Round Rose-Cut Black Spinel Gem (ID: 438864)
7.16 ct Spinel
12 mm
$ 21.48
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5.2ct Round Facet Brown Smoky Quartz Gem (ID: 463935)
5.24 ct Smoky Quartz
11.7 mm
$ 7.86
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9.6ct Round Cabochon Gray Blue Sheen Labradorite Gem (ID: 489596)
9.64 ct Labradorite
12.2 mm
$ 9.74
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8ct Round Cabochon Green Jadeite Gem (ID: 470588)
8.04 ct (total 16.07ctw) Jadeite
12.2 mm
$ 48.21
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8.3ct Round Cabochon White Quartz Cat's Eye Gem (ID: 369429)
8.33 ct (total 16.66ctw) Quartz Cat's Eye
12 mm
$ 53.98
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Click for Product Video (338287)
13.3ct Spherical Silver Pearl Gem (ID: 338287)
13.30 ct Pearl
12.3 mm
$ 199.50
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Click for Product Video (470800)
11ct Round Cabochon Grayish Silver Star Sapphire Gem (ID: 470800)
10.97 ct Star Sapphire
11.5 mm
$ 383.95
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7.3ct Round Rose-Cut Black Spinel Gem (ID: 438862)
7.33 ct Spinel
11.9 mm
$ 21.99
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7.6ct Round Cabochon Green Jadeite Gem (ID: 481240)
7.57 ct (total 15.14ctw) Jadeite
12.3 mm
$ 30.28
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Click for Product Video (335853)
13.3ct Spherical Golden Pearl Gem (ID: 335853)
13.34 ct Pearl
12.4 mm
$ 200.10
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Click for Product Video (338286)
13.7ct Spherical Silver Pearl Gem (ID: 338286)
13.72 ct Pearl
12.4 mm
$ 205.80
Item in Stock
Round Shape 12 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 Round shapes, facet cut and cabochon gems available now in 12 mm diameter 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 around 0.3 mm or slightly higher even. This small variance can usually be accommodated for 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.

Certified Customer Reviews
Overall Rating -> 9 star ratings
My selection was made quickly and efficiently.
Posted By JimC in November, 2018
Source: Bizrate
Overall Rating -> 10 star ratings
GemSelect has a great selection at reasonable prices. Gemstones are always as beautiful as pictured.
Posted By GemLover in November, 2018
Source: Bizrate
Overall Rating -> 10 star ratings
Colors and qualities of gems are very well represented online. Easy to use website. Great selections!
Posted By in November, 2018
Source: Bizrate
Overall Rating -> 10 star ratings
This was my second purchase from GemSelect and definitely won’t be my last! They have a very wide variety of gems and you can always find what you are looking for with ease and the prices are very good.
Posted By Jill in November, 2018
Source: Bizrate
Overall Rating -> 10 star ratings
Loved the wide selection of product
Posted By Miki in November, 2018
Source: Bizrate
Overall Rating -> 10 star ratings
finally bought the last rock to complete my ring idea; needed another white one after giving the big diamond to my daughter. a diamond that size is out of my retired-school-teacher budget, so i bought a white zircon. went back to the same place that i got my loose sapphire-- great selection, good prices, good delivery!
Posted By Ptcmom in November, 2018
Source: Bizrate
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All Gemstones (144)
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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