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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Gemstones A-Z

Buy Octagon Shape 20x15 mm Gems

3.86 carat Emerald Cut Emerald, loose Certified Emerald from Zambia, Natural Gem, 10.1 x 8.6 mm

2.37 ct Red Andesine Labradorite, 10.3 x 8.2 mm Oval Cut From Congo

4.12 carat Swiss Blue Topaz, Oval loose Topaz from Brazil, Natural Gems, 7.1 x 5.1 mm

1.36 ct Yellow Quartz, 9.1 x 4.5 mm Marquise Cut From Brazil

0.65 ct Loose Yellow Sapphire, 5.9 x 4 mm Oval Cut From Tanzania

12.53 ct Oval Boulder Opal, 17.8 x 13.7 mm From Australia

3.3 ct Green Agate, 10.2 x 8.4 mm Oval Cut From India

26.4 ct Odd Shaped Druzy Azurite, 22.6 x 17.5 mm From the United States

8.13 ct Carved Prehnite, 18.1 x 16.9 mm From South Africa

6.62 ct Yellow Quartz, 13.7 x 8.5 mm Octagon Cut From Brazil

28.45 ct Square Hematite, 17.2 x 16.3 mm From Brazil

0.74 carat Yellow Citrine, Heart loose Citrine from Brazil, Natural Untreated Gem, 6.1 x 6.1 mm

23.78 ct Fancy Chrysocolla, 22.8 x 22.6 mm From Australia

2.39 carat Yellow Citrine, Round loose Citrine from Brazil, Natural Untreated Gems, 7.1 mm

3.98 ct Green Agate, 16.9 x 8.8 mm Carved From India

1.11 carat Pear Shape Opal, loose Certified Opal from Australia, Natural Untreated Gem, 12 x 7.1 mm

1.42 carat Green Tourmaline, Emerald Cut loose Tourmaline from Mozambique, Natural Untreated Gem, 16.2 x 3.2 mm

9.11 ct Oval Nuummite, 15.1 x 12.6 mm From India

41.48 ct Oval Checkerboard Labradorite, 37.2 x 22.3 mm From Madagascar

5.73 carat Sky Blue Topaz, Emerald Cut loose Topaz from Brazil, Natural Gem, 10.1 x 9.9 mm

72.62 carat Cushion Amethyst, loose Certified Amethyst from Brazil, Natural Untreated Gem, 32.7 x 22.5 mm

12.4 ct Amethyst Geode Slice, 19.7 x 15.5 mm From Brazil

0.91 carat Pear Shape Peridot, loose Certified Peridot from China, Natural Untreated Gems, 6.1 x 4.1 mm

65.85 ct Baguette Ruby-Zoisite, 25.7 x 22.3 mm From Tanzania

1.48 carat Blue Tanzanite, Pear Shape loose Tanzanite from Tanzania, Natural Gems, 4.9 x 3.7 mm

2.59 ct Blue Kyanite, 9.5 x 7.1 mm Oval Cut From Nepal

1.36 ct Oval Cut Rainbow Moonstone, 8.9 x 6.9 mm From India

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

1.26 ct Green Apatite, 6.7 x 6.6 mm Asscher Cut From Madagascar

1.46 ct Purple Spinel, 6.3 x 6 mm Cushion Cut From Tanzania

25.01 ct Yellow Spinel, 17.6 x 8.2 mm Baguette Rose Cut From Thailand

10.77 carat Blue Green Turquoise, Pear loose Turquoise from the United States, Natural Gem, 19.3 x 14 mm

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