Calibrated Marquise Cut Gemstones in Size 12x6 mm

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 marquise shaped facet cut gems, gemstone carvings and cabochons available in 12 mm x 6 mm sizes. For the largest selection of colored gemstones, Shop GemSelect Online.

As a general guideline, when it comes to calibrated gems, they are not usually expected to be cut to exact measurements and specifications. But rather, they're cut with slight variance in size, though the close approximatation in size is not clearly defined, there are general guidelines for what is considered acceptable. Obviously larger and heavy carat weight stones allow more room in size for variance, while smaller stones may leave little to none. This means a large 30mm calibrated gemstone, could actually be closer to 31 millimeters. For this reason, we recommend to always view the exact size in addition to the calibrated size details. The exact size will inform you of the variance you can expect. Some setting styles are more flexible with variance, such as prong settings, while other styles of mountings may need almost an exact size to the fraction of millimeter.

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

Purchased for my granddaughter she was very pleased with it.

Posted By Charlie in April, 2024

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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.

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Overall Rating -> 10

Great selection

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Very large selection of items and we used the stones to have several pieces of jewelry made for us.

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Overall Rating -> 10

The website is easy to navigate and has a great selection. I am an amateur silver smith casting jewelry with stones

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Overall Rating -> 9

The selection and filtering is a little overwhelming, but that's only because there is so much to choose from.

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I am excited for my first order, search tools were a great help to find the sapphire I needed for my next project! Thank you

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love yall

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Easy to use. Limited supply of higher quality gemstones.

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Overall Rating -> 10

Everything fine.

Posted By Hilario in December, 2023

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Overall Rating -> 9

Not easy enough to buy by exact size, and many stones aren't carbechon curved shape on top

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Gemstones A-Z

Buy Marquise Shape 12x6 mm Gems

16.75 ct Fancy Fossil Coral, 20.8 x 10.6 mm From Indonesia

0.81 carat Heart Cabochon Amethyst, loose Certified Amethyst from Brazil, Natural Untreated Gem, 6 x 5.7 mm

1.24 carat Green Tourmaline, Emerald Cut loose Tourmaline from Mozambique, Natural Untreated Gem, 16.2 x 3.7 mm

0.3 ct Baguette Cut Iolite, 5 x 3 mm From Madagascar

0.75 carat Green Tourmaline, Emerald Cut loose Tourmaline from Tanzania, Natural Untreated Gem, 12.2 x 2.9 mm

2.65 ct Green Sphene, 8.2 x 7.4 mm Oval Cut From Sri Lanka

0.45 carat Orange Spessartite Garnet, Oval loose Spessartite Garnet from Mozambique, Natural Untreated Gem, 5 x 3.3 mm

48.64 ct Oval Jasper, 28.9 x 25.4 mm From Mexico

42.53 ct Yellow Aventurine, 40.8 x 11.6 mm Pencil Cut From Brazil

1.53 carat Yellow Citrine, Heart loose Citrine from Brazil, Natural Untreated Gems, 6.1 x 6 mm

0.54 ct Octagon Cut Peridot, 6 x 4 mm From China

4.23 carat White Zircon, Diamond-Cut loose Zircon from Cambodia, Natural Gems, 6 mm

1.1 ct Orange Sphalerite, 5.9 mm Round Cut From Spain

2.19 carat Blue Sapphire, Princess-Cut loose Sapphire from Sri Lanka, Natural Gems, 2.3 x 2.2 mm

2.16 ct Oval Sillimanite Cat's Eye, 7.3 x 4.8 mm From Madagascar

3.73 carat Marquise Cut Pyrope Garnet, loose Certified Pyrope Garnet from Mozambique, Natural Untreated Gems, 12 x 6.2 mm

7.94 carat Yellow Citrine, Briolette loose Citrine from Brazil, Natural Untreated Gem, 15.2 mm

94.11 ct Yellow Quartz, 32.4 x 26.4 mm Oval Portuguese Cut From Brazil

24.67 ct Square Hematite, 16.6 x 15.4 mm From Brazil

31.7 ct Oval Charoite, 29.2 x 19.4 mm From Russia

2.88 ct Loose Baguette Labradorite, 9 x 7.1 mm From Madagascar

1 carat Pear Shape Color-Change Diaspore, loose Certified Color-Change Diaspore from Turkey, Natural Untreated Gem, 10.2 x 4.5 mm

0.46 ct Loose Yellow Sapphire, 3.1 x 3.1 mm Princess Cut From Tanzania

4.97 carat Green Tourmaline, Carved Leaf loose Tourmaline from Mozambique, Natural Untreated Gem, 15.7 x 9.3 mm

19.6 carat Black Tourmaline, Oval loose Tourmaline from Tanzania, Natural Untreated Gem, 19.8 x 16.5 mm

7.6 carat Pear Shape Amethyst, loose Certified Amethyst from Brazil, Natural Untreated Gem, 16 x 12 mm

33.09 ct Fancy Dendritic Agate, 25.6 x 22.9 mm From India

1.77 carat Orange Hessonite Garnet, Emerald Cut loose Hessonite Garnet from Madagascar, Natural Untreated Gem, 7 x 6.9 mm

0.94 carat Round Sapphire, loose Certified Sapphire from Tanzania, Natural Gems, 4 mm

6.09 ct Rainbow Pyrite, 14.7 x 14.4 mm From Russia

28.78 carat Swiss Blue Topaz, Pear Shape loose Topaz from Brazil, Natural Gem, 22.2 x 15.6 mm

2.41 carat Swiss Blue Topaz, Pear Shape loose Topaz from Brazil, Natural Gems, 6.2 x 4.2 mm

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