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Montana Agate Cabochons

Pretty semi precious gemstone Montana Agate comes from Montana.

It comes from near the Yellowstone River.

Montana Agate is one of the alluvial agates, it is not found in-site, but in the Flaxville gravel deposits scattered over a huge area encompassing thousands of square miles. Montana Moss Agate is found throughout the 670 mile length of the river.

The agate originally was formed in the Yellowstone National Park area of Wyoming as a result of volcanic activity approximately 65 million years ago.

In Montana Agate cabochons the red color is the result of iron oxide, the black and brown is the result of manganese oxide and the red and orange came from iron oxide. On very rare occasions you can get a green from copper. 

It is considered a moss agate because of the mossy shape of its inclusions, but more often it is banded, polka dotted or has dendrites.

Most of the Montana Agate rough is broken up and found in smaller pieces.  Chunks larger than 10 pounds are rare.  However the largest piece ever found weighed 63.5 pounds! 

Montana Agate generally has a coating or skin.

Agate is a microcrystalline Quartz and has a hardness of 7, which makes the Montana Agate designer cabochons very wearable.

Montana Agate has been the state of Montana's official state gemstone (along with Montana Sapphire) since 1969.

  • Montana Agate Matched Pairs Freeforms Cabochons Stones #18 Montana Agate Matched Pairs Freeforms Cabochons Stones #18

    Montana Agate Matched Pair Cabochons #18

    Freeform shaped matched pair milky translucent with black and brown spots semi precious gemstone Montana Agate designer cabochons 24.5 mm by 10 mm and 4 mm thick. These weigh about 5 carats each. Pretty semi precious gemstone Montana Agate comes...

    $36.00
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  • Montana Agate Matched Pairs Translucent Cabochons Stones #17 Montana Agate Matched Pairs Translucent Cabochons Stones #17

    Montana Agate Matched Pair Cabochons #17

    Thin oval shaped matched pair milky translucent with black and brown spots semi precious gemstone Montana Agate designer cabochons 24.5 mm by 8 mm and 3.5 mm thick. These weigh about 5 carats each. Pretty semi precious gemstone Montana Agate comes...

    $36.00
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  • Montana Agate Matched Pairs Triangles Cabochons Stones #23 Montana Agate Matched Pairs Triangles Cabochons Stones #23

    Montana Agate Matched Pair Cabochons #23

    Triangle shaped matched pair milky translucent with black and brown spots semi precious gemstone Montana Agate designer cabochons 32 mm by 11 mm and 4 mm thick. These weigh about 56. carats each. Pretty semi precious gemstone Montana Agate...

    $40.00
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  • Montana Agate Matched Pairs Gemstones Cabochons Stones #16 Montana Agate Matched Pairs Gemstones Cabochons Stones #16

    Montana Agate Matched Pair Cabochons #16

    Triangle shaped matched pair milky translucent with black spots semi precious gemstone Montana Agate designer cabochons 34.5 mm by 10 mm and 4 mm thick. These weigh about 6.5 carats each. Pretty semi precious gemstone Montana Agate comes from...

    $48.00
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  • Montana Agate Translucent Polka Dotted Oval Cabochon #2 Montana Agate Translucent Polka Dotted Oval Cabochon #2

    Montana Agate Cabochon #2

    Milky but very translucent with black and brown spots oval shaped Montana Agate designer cabochon 28 mm long by 15 mm wide and 4 mm thick. Pretty semi precious gemstone Montana Agate comes from near the Yellowstone River in Montana. In...

    $18.00
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  • Montana Agate Large Matched Pair Cabochons High Grade #24 Montana Agate Large Matched Pair Cabochons High Grade #24

    Montana Agate Matched Pair Cabochons #24

    Long thin trapezoid shaped High Grade matched pair milky translucent with black semi precious gemstone Montana Agate designer cabochons 56 mm by 4 to 14 mm and 4 mm thick. These weigh about 18.5 carats each. Pretty semi precious gemstone...

    $125.00
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  • Montana Agate Matched Pair Cabochons High Grade #22 Montana Agate Matched Pair Cabochons High Grade #22

    Montana Agate Matched Pair Cabochons #22

    Long thin triangle shaped High Grade matched pair milky translucent with black semi precious gemstone Montana Agate designer cabochons 64 mm by 11 mm and 4 mm thick. These weigh about 16 carats each. Pretty semi precious gemstone Montana...

    $125.00
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  • Montana Agate Matched Pair Cabochons Polka Dot #13 Montana Agate Matched Pair Cabochons Polka Dot #13

    Montana Agate Matched Pair Cabochons #13

    Trapezoid shaped matched pair milky translucent with black polka dots semi precious gemstone Montana Agate designer cabochons 22 mm long by 5 to 11 mm wide and 3 mm thick. These weigh about 5 carats each. Pretty semi precious gemstone Montana...

    $30.00
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  • Montana Agate Matched Pair Cabochons Translucent #2 Montana Agate Matched Pair Cabochons Translucent #2

    Montana Agate Matched Pair Cabochons #2

    Round shaped matched pair milky translucent with black semi precious gemstone Montana Agate designer cabochons 18 mm in diameter and 3 mm thick. These weigh about 9 carats each. Pretty semi precious gemstone Montana Agate comes from near...

    $36.00
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  • Matched Pair Cabochons for Jewelry Design Montana Agate #20 Matched Pair Cabochons for Jewelry Design Montana Agate #20

    Montana Agate Matched Pair Cabochons #20

    Small trapezoid shaped matched pair milky translucent with black spots semi precious gemstone Montana Agate designer cabochons 16 mm by 8 to 13 mm and 4 mm thick. These weigh about 5.5 carats each. Pretty semi precious gemstone...

    $18.00
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  • Montana Agate Matched Pair Cabochons Designer #20 Montana Agate Matched Pair Cabochons Designer #20

    Montana Agate Matched Pair Cabochons #21

    Trapezoid shaped matched pair milky translucent with black semi precious gemstone Montana Agate designer cabochons 23 mm 5.5 to 10 mm and 4 mm thick. These weigh about 6 carats each. Pretty semi precious gemstone Montana Agate comes from near...

    $36.00
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  • Montana Agate Matched Pair Cabochons Designer #5 Montana Agate Matched Pair Cabochons Designer #5

    Montana Agate Matched Pair Cabochons #5

    Round shaped matched pair milky translucent with black semi precious gemstone Montana Agate designer cabochons 21 mm in diameter and 4 mm thick. These weigh about 13 carats each. Pretty semi precious gemstone Montana Agate comes from...

    $40.00
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  • Montana Agate Matched Pair Cabochons Designer #19 Montana Agate Matched Pair Cabochons Designer #19

    Montana Agate Matched Pair Cabochons #19

    Round shaped matched pair milky translucent with black semi precious gemstone Montana Agate designer cabochons 18 mm in diameter and 3 mm thick. These weigh about 8.5 carats each. Pretty semi precious gemstone Montana Agate comes from...

    $36.00
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  • Montana Agate Matched Pair Cabochons Designer #15 Montana Agate Matched Pair Cabochons Designer #15

    Montana Agate Matched Pair Cabochons #15

    Round shaped matched pair milky translucent with black semi precious gemstone Montana Agate designer cabochons 15.5 mm in diameter and 4 mm thick. These weigh about 7 carats each. Pretty semi precious gemstone Montana Agate comes from...

    $24.00
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  • Montana Agate Matched Pair Cabochons Designer #7 Montana Agate Matched Pair Cabochons Designer #7

    Montana Agate Matched Pair Cabochons #7

    Trapezoid shaped matched pair milky translucent with black polka dots semi precious gemstone Montana Agate designer cabochons 22 mm long by 7 to 12 mm wide and 4 mm thick. These weigh about 7 carats each. Pretty semi precious gemstone...

    $30.00
    Add to Cart
  • Montana Agate Matched Pair Cabochons Designer #4 Montana Agate Matched Pair Cabochons Designer #4

    Montana Agate Matched Pair Cabochons #4

    Triangle shaped matched pair milky translucent with black polka dots semi precious gemstone Montana Agate designer cabochons 22 mm by 15 mm and 3.5 mm thick. These weigh about 8 carats each. Pretty semi precious gemstone Montana Agate...

    $36.00
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  • Montana Agate Cabochon #17 Montana Agate Cabochon #17

    Montana Agate Cabochon #17

    Oval shaped translucent with black and brown inclusions semi precious gemstone Montana Agate designer cabochon 38 mm by 19 mm by 6 mm thick. Pretty semi precious gemstone Montana Agate comes from near the Yellowstone River in Montana. In...

    $30.00
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  • Montana Agate Matched Pair Cabochons #6 Montana Agate Matched Pair Cabochons #6

    Montana Agate Matched Pair Cabochons #6

    Oval shaped matched pair milky translucent with black spots semi precious gemstone Montana Agate designer cabochons 15 mm in diameter and 3.5 mm thick. These weigh about 7.5 carats each. Pretty semi precious gemstone Montana Agate comes...

    $36.00
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  • Montana Agate Matched Pair Cabochons #11

    Montana Agate Matched Pair Cabochons #11

    Trillion or triangle shaped matched pair milky translucent with black semi precious gemstone Montana Agate designer cabochons with 20 mm sides and 5 mm thick. These weigh about 13 carats each. Pretty semi precious stone Montana Agate comes...

    $36.00
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  • translucent with black semi prescious gemstone Montana Agate designer cabochon Montana Agate Cabochon #13

    Montana Agate Cabochon #13

    Oval shaped milky translucent with black semi precious gemstone Montana Agate designer cabochon 29 mm by 23 mm by 6 mm. Pretty semi precious gemstone Montana Agate comes from near the Yellowstone River in Montana. In Montana Agate cabochons...

    $18.00
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  • translucent with black semi prescious gemstone Montana Agate designer cabochon translucent with black semi prescious gemstone Montana Agate designer cabochon

    Montana Agate Cabochon #3

    Oval shaped milky translucent with black semi precious gemstone Montana Agate designer cabochon 32 mm by 19 mm by 5 mm. Pretty semi precious gemstone Montana Agate comes from near the Yellowstone River in Montana. In Montana Agate cabochons the red...

    $35.00
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  • matched pair milky translucent with black semi precious gemstone Montana Agate designer cabochons Montana Agate Matched Pair Cabochons #9

    Montana Agate Matched Pair Cabochons #9

    Trillion or triangle shaped matched pair milky translucent with black semi precious gemstone Montana Agate designer cabochons with 20 mm sides and 4 mm thick. These weigh about 10 carats each. Pretty semi precious gemstone Montana Agate comes...

    $36.00
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  • matched pair milky translucent with black semi precious gemstone Montana Agate designer cabochons matched pair milky translucent with black semi precious gemstone Montana Agate designer cabochons

    Montana Agate Matched Pair Cabochons #10

    Oval shaped matched pair milky translucent with black semi precious gemstone Montana Agate designer cabochons 20 mm by 14 mm and 4 mm thick. These weigh about 9.5 carats each. Pretty semi precious gemstone Montana Agate comes from near the...

    $36.00
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  • Montana Agate Cabochon #8 Montana Agate Cabochon #8

    Montana Agate Cabochon #8

    Freeform shield shaped milky translucent with black and brown semi precious gemstone Montana Agate designer cabochon 31 mm wide by 25 mm long and 5 mm thick. Pretty semi precious stone Montana Agate comes from near the Yellowstone River in Montana...

    $25.00
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