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 -> 9

making my own jewelry for my birth stone

Posted By LoveGeo in July, 2023

Source: Bizrate

Overall Rating -> 10

I bought a small ring green so I may practice my jewelry making.

Posted By HairyOtter in July, 2023

Source: Bizrate

Overall Rating -> 9

So many gorgeous stones! The only "complaint" I have is it's difficult to visualize sizes in mm. Perhaps some way to compare in inches?It has been a long time since I bought stones from Gem select, but the process wasn't too difficult.

Posted By Ktreva52 in February, 2024

Source: Bizrate

Overall Rating -> 10

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

Posted By C.J. in February, 2024

Source: Bizrate

Overall Rating -> 10

Wonderful selection of gems to choose from. Have made many purchases and was only slightly disappointed once.

Posted By Teemo in February, 2024

Source: Bizrate

Overall Rating -> 10

This is only the second time I have ordered from GemSelect. I am a prolific gemstone collector and I wish I had found this site sooner!

Posted By Beachcomber in September, 2023

Source: Bizrate

Overall Rating -> 9

GemSelect has a fantastic assortment of Semi-precious stones. I have not found any other web site with the variety you have.

Posted By RobDill in August, 2023

Source: Bizrate

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

Source: Bizrate

Overall Rating -> 10

Easy and fast

Posted By Mark in February, 2024

Source: Bizrate

Overall Rating -> 10

Everthing about researching and ordering from Gemselect was easy and uncomplicated. In the past I had payment problems, but your customer rep, Thomas, helped me get everything right. I will continue using Gemselet in the future for these reasons.

Posted By WildwillyfromArizona in August, 2023

Source: Bizrate

Overall Rating -> 10

The gem stone always has a great selection of beautiful stones. The calibrated stone fit my ring perfectly. Thank you gem select !

Posted By Jen in August, 2023

Source: Bizrate

Overall Rating -> 10

great. thank you

Posted By Carrotroller in July, 2023

Source: Bizrate

Overall Rating -> 10

Convenient selection, arrival on time

Posted By Alin in February, 2024

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Overall Rating -> 10

Great website and information

Posted By Moonshot in December, 2023

Source: Bizrate

Overall Rating -> 9

It was simple and clear to understand.

Posted By Thora007 in December, 2023

Source: Bizrate

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Gemstones A-Z

Buy Octagon Shape 20x15 mm Gems

5.59 carat Yellow Citrine, Round loose Citrine from Brazil, Natural Untreated Gem, 11.8 mm

2.91 carat White Topaz, Cushion loose Topaz from Brazil, Natural Untreated Gems, 4.6 x 4.5 mm

6.18 carat Black Tourmaline, Emerald Cut loose Tourmaline from Mozambique, Natural Untreated Gem, 17.3 x 6.7 mm

0.66 carat Orange Spessartite Garnet, Pear Shape loose Spessartite Garnet from Mozambique, Natural Untreated Gem, 6.8 x 4 mm

2.8 carat Trillion Amethyst, loose Certified Amethyst from Brazil, Natural Untreated Gem, 10.1 x 10 mm

10.22 ct Octagon Cut Smoky Quartz, 13.5 x 13.5 mm From Brazil

1.52 carat Square Rhodolite Garnet, loose Certified Rhodolite Garnet from Mozambique, Natural Untreated Gems, 5.1 x 5 mm

18.68 ct Rainbow Pyrite, 23.2 x 16.2 mm From Russia

0.77 carat Yellow Citrine, Pear Shape loose Citrine from Brazil, Natural Gem, 7.7 x 5 mm

1.46 carat White Zircon, Diamond-Cut loose Zircon from Myanmar, Natural Gems, 5 mm

26.52 carat Green Fluorite, Oval loose Fluorite from India, Natural Untreated Gem, 17.7 x 16.1 mm

29.86 ct Pencil Cut Jasper, 32.3 mm From India

2.78 ct Yellow Beryl, 10.8 x 8.8 mm Oval Cut From Brazil

23.02 ct Oval Fossil Coral, 18.4 x 12.4 mm From Indonesia

12.08 ct Round Rutile Quartz, 16.3 mm From India

1.46 carat Orange Hessonite Garnet, Oval loose Hessonite Garnet from Madagascar, Natural Untreated Gem, 7.5 x 6.2 mm

0.71 carat Oval Tsavorite Garnet, loose Certified Tsavorite Garnet from Tanzania, Natural Untreated Gem, 6.1 x 5.2 mm

26.88 carat Oval Amethyst, loose Certified Amethyst from Brazil, Natural Untreated Gem, 20.1 x 17.2 mm

3.2 carat Trillion Amethyst, loose Certified Amethyst from Brazil, Natural Untreated Gem, 10.1 x 9.9 mm

1.38 ct Oval Cut Peridot, 8.2 x 6.2 mm From China

15.46 carat Carved Rose Amethyst, loose Certified Amethyst from Brazil, Natural Untreated Gem, 16.2 x 15.2 mm

1.56 ct Purple Spinel, 6.3 x 6.3 mm Cushion Cut From Tanzania

0.42 ct Loose Pink Sapphire, 6.1 x 4.4 mm Odd Shaped From Tanzania

6.66 carat Marquise Cut Amethyst, loose Certified Amethyst from Brazil, Natural Untreated Gem, 18.2 x 9.2 mm

1.18 ct Oval Cut Fire Opal, 8.9 x 7.3 mm From Mexico

0.66 ct Loose Yellow Sapphire, 4.5 x 4.5 mm Cushion Cut From Tanzania

1.82 carat White Zircon, Diamond-Cut loose Zircon from Cambodia, Natural Gem, 6.8 mm

0.78 carat Pear Tiger's Eye, loose Certified Tiger's Eye from Thailand, Natural Untreated Gem, 6.1 x 5.7 mm

1.28 carat Orange Hessonite Garnet, Baguette Cut loose Hessonite Garnet from Madagascar, Natural Untreated Gem, 6.8 x 5 mm

13.53 carat Cushion Amethyst, loose Certified Amethyst from Brazil, Natural Untreated Gem, 15 x 15 mm

1.76 ct Yellow Sphene, 7.7 x 6.1 mm Oval Cut From Sri Lanka

2.7 carat Pink Tourmaline, Oval loose Tourmaline from Mozambique, Natural Untreated Gem, 9.1 x 7.2 mm

Gemstone Information

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