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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Interested in unusual stones and found many that I purchased or will purchase in the near future. I have been a customer of gem select for almost ten years and have always been pleased with buying experience and the delivered product

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I had a great time searching all the lovely stones. This is my first precious loose stone purchase for my own work. I chose sapphire, and found some lovely briolettes. I wanted 3, but this set of 4 was perfect. Everything was quick and easy, and I'm excited.

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I was looking for ammolite for my husband. Other websites are not always clear about whether they have genuine ammolite or simulated ammolite. I have purchased from GemSelect before and trust that the stones are genuine. Finding the stones I want is easy, and I love all of the search filter options!

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Gemstones A-Z

Buy Marquise Shape 12x6 mm Gems

0.66 ct Loose Yellow Sapphire, 4.8 mm Round Cut From Tanzania

3.99 ct Fancy Fire Agate, 14.2 x 9 mm From Mexico

4.78 carat Yellow Citrine, Briolette loose Citrine from Brazil, Natural Untreated Gem, 12.8 mm

2.14 ct Yellow Quartz, 9.2 x 9.1 mm Carved From Brazil

2.23 carat Orange Spessartite Garnet, Round loose Spessartite Garnet from Mozambique, Natural Untreated Gems, 4.4 mm

18.42 ct Fancy Boulder Opal, 22.4 x 14.5 mm From Australia

20.3 ct Black Spinel, 16.1 x 11.8 mm Oval Rose Cut From Thailand

6.05 carat Pear Rutile Quartz, loose Certified Rutile Quartz from India, Natural Untreated Gem, 14.8 x 10.9 mm

65.53 ct Round Hematite, 20.1 mm From Brazil

0.36 ct Loose Yellow Sapphire, 5.1 x 2.6 mm Marquise Cut From Tanzania

0.88 ct Loose Orange Sapphire, 6.1 x 4.9 mm Oval Cut From Tanzania

1.56 carat Orange Hessonite Garnet, Oval loose Hessonite Garnet from Madagascar, Natural Untreated Gem, 7.8 x 6.5 mm

1.37 carat Yellow Citrine, Trillion loose Citrine from Brazil, Natural Untreated Gems, 6.1 x 5.9 mm

0.53 carat Trillion Rhodolite Garnet, loose Certified Rhodolite Garnet from Mozambique, Natural Untreated Gem, 5.2 x 5.1 mm

1.42 carat Orange Hessonite Garnet, Square loose Hessonite Garnet from Madagascar, Natural Untreated Gem, 6.4 x 6.3 mm

23.33 ct Oval Quartz With Marcasite, 23.3 x 16.6 mm From Brazil

17.77 carat Oval Amethyst, loose Certified Amethyst from Brazil, Natural Untreated Gem, 20.4 x 16.7 mm

5.39 carat Oval Amethyst, loose Certified Amethyst from Brazil, Natural Untreated Gem, 13.5 x 10.8 mm

1.62 carat Orange Hessonite Garnet, Emerald Cut loose Hessonite Garnet from Madagascar, Natural Untreated Gem, 6.1 x 6.1 mm

26.19 carat Bi-color Ametrine, Oval loose Ametrine from Brazil, Natural Untreated Gem, 22.1 x 16.3 mm

42.68 ct Oval Snowflake Obsidian, 35.6 x 22.1 mm From India

9.81 ct Flower Cut Smoky Quartz, 11.4 x 10.1 mm From Brazil

2.09 carat White Zircon, Oval loose Zircon from Cambodia, Natural Gems, 6.9 x 5.1 mm

23.85 ct Baguette Maw-Sit-Sit, 16.9 x 11.7 mm From Myanmar

22.96 ct Gray Jadeite, 27.8 x 14.2 mm Oval Cut From Myanmar

7.49 ct Octagon Cut Smoky Quartz, 11.6 x 11.6 mm From Brazil

20.48 ct Baguette Hematite, 18.1 x 13 mm From Brazil

16.57 ct Loose Pear Dendritic Agate, 18.2 x 13.2 mm From India

2.34 carat Marquise Cut Amethyst, loose Certified Amethyst from Brazil, Natural Untreated Gems, 5.9 x 3 mm

3.22 carat Yellow Citrine, Emerald Cut loose Citrine from Brazil, Natural Untreated Gems, 7.9 x 6.1 mm

0.76 ct Loose Violet Sapphire, 6.6 x 4.8 mm Oval Cut From Madagascar

0.9 carat Oval Peridot, loose Certified Peridot from China, Natural Untreated Gem, 7.2 x 5.2 mm

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