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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Overall Rating -> 10

Very detailed and great pictures

Posted By Alexandrite in November, 2023

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Overall Rating -> 10

I was looking for a source for affordable genuine gemstones for my grandson who is currently very interested in rocks and gems. I was quite surprised and pleased to find GemSelect and finding the right stones at the right price couldn't have been simpler.

Posted By Papa in December, 2023

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Overall Rating -> 9

I was in the market for birthstones for a lil gift project im doing. I'm no expert in gems or what not but the quality as far as i can tell seems to be spot on.

Posted By PixelComposer in January, 2024

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Overall Rating -> 10

Fine. All emails answered. Excellent service. Nice discount added for orders. Briefly, a very good experience.

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Overall Rating -> 10

Website was incredibly easy and fast to use. Navigation and product outlay was simple and enjoyable to browse. Thank you and have a blessed day!

Posted By Devi in October, 2023

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Overall Rating -> 10

all good

Posted By John in December, 2023

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Overall Rating -> 10

Purchasing from Gem Select was a pleasant and easy experience. The photos of the stones I was interested in were an accurate depiction of the stones I received. Ordering was easy and the items arrived within a week. Over all it was a very positive experience.

Posted By Dee in September, 2023

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Overall Rating -> 10

Very pleased with shopping on this site. It's easy to navigate and information about gemstones is very good.

Posted By Kate in December, 2023

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Overall Rating -> 9

My first purchase went well. I will purchase more gems in the future.

Posted By NoHalalAl in March, 2024

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Overall Rating -> 10

Great Job today! No issues!

Posted By Samlovesgems777 in August, 2023

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Overall Rating -> 9

They had a easy to navigate directory for all the currently available products. You could filter by almost any parameter you could think of. The checkout process was smooth and painless, and the shipping was quick and efficient. All-in-all, it was a very positive experience.

Posted By Brian in May, 2024

Source: Bizrate

Overall Rating -> 10

I have used GemSelect for several years and plan to shop more in the further. This is a good source of information on gemstones. I love looking at and learning about them. Lot more than I ever knew existed.

Posted By Bikerwalrus in October, 2023

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Overall Rating -> 10

Very Good

Posted By Julian in July, 2023

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Overall Rating -> 10

Had a problem ordering first time. Someone from Gem Select reached out to me and cleared problem and I made purchase.

Posted By Myrtle in February, 2024

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Overall Rating -> 10

Great selection, I love your site! Great product visibility, information, etc.

Posted By John in February, 2024

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Gemstones A-Z

Buy Octagon Shape 20x15 mm Gems

4.87 carat Yellow Citrine, Round Drilled Checkerboard loose Citrine from Brazil, Natural Untreated Gem, 11.1 mm

6.14 carat Sky Blue Topaz, Oval loose Topaz from Brazil, Natural Gems, 10 x 7.9 mm

1.55 ct Oval Cut Kornerupine, 9.1 x 6.2 mm From Sri Lanka

3.59 carat Sky Blue Topaz, Marquise Cut loose Topaz from Brazil, Natural Gem, 15 x 7 mm

11.84 carat Pink Topaz, Oval loose Topaz from Brazil, Natural Gems, 12.2 x 10.2 mm

4.69 carat London Blue Topaz, Heart loose Topaz from Brazil, Natural Gem, 10.4 x 9.9 mm

3.15 ct Round Checkerboard Smoky Quartz, 8 mm From Brazil

1.39 carat Square Rhodolite Garnet, loose Certified Rhodolite Garnet from Mozambique, Natural Untreated Gems, 5.1 x 5.1 mm

1.55 carat Orange Zircon, Emerald Cut loose Zircon from Tanzania, Natural Untreated Gem, 7.1 x 4.9 mm

7.46 carat Green Agate, Pear loose Agate from India, Natural Gem, 14.2 x 11.7 mm

6.25 carat Swiss Blue Topaz, Carved Leaf loose Topaz from Brazil, Natural Gem, 11.6 x 9.3 mm

0.94 ct Loose Round Pietersite, 7.2 mm From Namibia

1.01 ct Blue Kyanite, 7.1 x 5 mm Oval Cut From Nepal

25.08 ct Oval Howlite, 29.6 x 20.5 mm From the United States

18.53 ct Trillion Jasper, 18.5 x 18.5 mm From Indonesia

6.32 carat Orange Zircon, Round loose Zircon from Sri Lanka, Natural Untreated Gems, 4.5 mm

6.93 carat Swiss Blue Topaz, Carved Leaf loose Topaz from Brazil, Natural Gem, 14.6 x 11.4 mm

2.73 carat Marquise Cut Pyrope Garnet, loose Certified Pyrope Garnet from Mozambique, Natural Untreated Gems, 10.1 x 5.1 mm

2.17 carat White Zircon, Oval loose Zircon from Cambodia, Natural Gems, 7.1 x 5.1 mm

43.9 ct Drilled Sphere Rhodochrosite, 16.5 mm From South Africa

1.4 ct Yellow Beryl, 7.9 mm Round Cut From Madagascar

3.7 carat Yellow Citrine, Oval loose Citrine from Brazil, Natural Untreated Gem, 11 x 9 mm

8.84 ct Oval Buff Top Chalcedony, 11.9 x 9.9 mm From Brazil

0.88 carat Sky Blue Topaz, Pear Shape loose Topaz from Brazil, Natural Gem, 7.1 x 5.2 mm

0.83 carat Oval Emerald, loose Certified Emerald from Colombia, Natural Gem, 6.3 x 5.3 mm

2.31 carat Swiss Blue Topaz, Oval loose Topaz from Brazil, Natural Gems, 6.9 x 5 mm

1.15 ct Loose Multicolor Sapphire, 5.7 x 5.7 mm Cushion Cut From Madagascar

0.89 carat Pear Shape Peridot, loose Certified Peridot from China, Natural Untreated Gems, 6 x 4.1 mm

2.23 carat Sky Blue Topaz, Round loose Topaz from Brazil, Natural Gem, 8.1 mm

2.17 ct Loose Yellow Sapphire, 4.9 mm Round Cut From Tanzania

5.17 carat Yellow Citrine, Oval loose Citrine from Brazil, Natural Untreated Gems, 10 x 8 mm

8.24 carat Black Tourmaline, Oval loose Tourmaline from Mozambique, Natural Untreated Gem, 14.3 x 11.3 mm

Gemstone Information

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