Calibrated 20 x 15 mm Octagon Shape Natural Gemstones: GemSelect

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 20 x 15 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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Gemstone Information

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Overall Rating -> 7

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Overall Rating -> 10

i love this site, the gems are always of good quality, i've been buy gifts from the site for 10 years, love it

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Overall Rating -> 10

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Overall Rating -> 10

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Overall Rating -> 8

Very easy to find the specific stone I was looking for. I am pleased by both the selection and the price of the stones that are available. The only "bad" thing that I have to say is that the interface of the site is outdated.

Posted By Nick in March, 2024

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Overall Rating -> 10

Perfect size I was looking for and great price

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Overall Rating -> 10

Easy to use website, made it very easy to buy. Will shop here again.

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Overall Rating -> 10

i love this site, the gems are always of good quality, i've been buy gifts from the site for 10 years, love it

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Overall Rating -> 10

the searching format was easy to find what i needed. It helped to be able to sort Lowest price to Highest because i wasnt looking to spend too much but i did want an actual stone and not imitation.

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Overall Rating -> 10

GemSelect has the Best gems. Clear photos and detailed description helps me make the best choice. I have Never been disappointed by thier quality items.

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Never bought anything on this website before, but it probably won't be my last purchase. Definitely one of the easiest to use and most informative sites I've ever been to.

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Overall Rating -> 10

The website design is a bit finicky for mobile, but Im sure its most likely just a mobile issue. Amazing selection of products, great prices.

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Gemstones A-Z

Buy Octagon Shape 20x15 mm Gems

4.13 ct Pink Mystic Topaz, 9.8 mm Round Cut From Brazil

4.46 carat White Zircon, Oval loose Zircon from Cambodia, Natural Gems, 6.2 x 4.1 mm

2.01 ct Marquise Tiger's Eye, 11.8 x 5.9 mm From Thailand

34.48 ct Oval Pietersite, 30.2 x 22.2 mm From Namibia

1.01 ct Blue Kyanite, 6.9 x 5 mm Oval Cut From Nepal

1.81 ct Oval Cut Peridot, 7.1 x 5 mm From China

1.44 carat Multicolor Opal, Oval loose Opal from Ethiopia, Natural Gems, 7.7 x 5.9 mm

0.53 ct Orange Sphalerite, 4.7 mm Round Cut From Spain

6.74 ct Yellow Quartz, 8.9 x 8.6 mm Carved From Brazil

4.85 ct Asscher Cut Rose Quartz, 9 x 9 mm From South Africa

7.88 carat Oval Amethyst, loose Certified Amethyst from Brazil, Natural Untreated Gems, 11.2 x 9 mm

1.64 ct Oval Sillimanite Cat's Eye, 7.7 x 5.4 mm From Madagascar

4.43 carat Sky Blue Topaz, Pear Shape loose Topaz from Brazil, Natural Gems, 7.1 x 5 mm

0.62 carat Blue Topaz, Oval loose Topaz from Brazil, Natural Gem, 6 x 4 mm

1 carat Purple Spinel, Pear Shape loose Spinel from Tanzania, Natural Untreated Gem, 7.8 x 5.4 mm

0.4 carat Round Ruby, loose Certified Ruby from Myanmar, Natural Gem, 4 mm

10.22 ct Round Concave Cut Smoky Quartz, 12.1 mm From Brazil

0.3 carat Pink Sapphire, Pear Shape loose Sapphire from Madagascar, Natural Gem, 5.7 x 3.8 mm

17.1 carat Blue Topaz, Oval loose Topaz from Brazil, Natural Gem, 18.1 x 13 mm

19.33 carat Round Checkerboard Amethyst, loose Certified from Brazil, Natural Untreated Gem, 18.1 mm

1.06 carat Round Ruby, loose Certified Ruby from Myanmar, Natural Gem, 6 mm

3.15 ct Green Agate, 17.9 x 8.7 mm Carved From India

3.27 ct Round Petal Cut Smoky Quartz, 9.4 mm From Brazil

2.18 carat London Blue Topaz, Oval loose Topaz from Brazil, Natural Gem, 8.9 x 6.9 mm

2.62 carat Square Pyrope Garnet, loose Certified Pyrope Garnet from Mozambique, Natural Untreated Gems, 5.1 x 5 mm

0.69 carat Emerald Cut Emerald, loose Certified Emerald from Colombia, Natural Gem, 5.9 x 4.2 mm

0.44 carat Orange Sapphire, Pear Shape loose Sapphire from Tanzania, Natural Gem, 4.8 x 4.6 mm

0.53 ct Loose Yellow Sapphire, 6 x 5.2 mm Oval Cut From Tanzania

2.96 carat Red Zircon, Oval loose Zircon from Tanzania, Natural Untreated Gem, 9.5 x 6.9 mm

2.25 carat Princess-Cut Amethyst, loose Certified Amethyst from Brazil, Natural Untreated Gem, 8.1 x 8 mm

2.71 carat White Opal, Oval loose Opal from Australia, Natural Untreated Gem, 13.3 x 9.6 mm

0.4 ct Blue Apatite, 3.5 mm Round Cut From Madagascar

Gemstone Information

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