Montana Agate Cabochons

Pretty semi precious gemstone Montana Agate comes from near the Yellowstone River in Montana. 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 s and orange came from iron oxide. On very rare occassions you can get a green from copper.  It is considered a moss agate because of the mossy shape of its inclusions, but often it is banded, polka dotted or has dendrites.

Most of the Monatana 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!  The 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. Pretty semi precious gemstone Montana Agate comes from near the Yellowstone River in...

    $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. Pretty semi precious gemstone Montana Agate comes from near the Yellowstone River...

    $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. Pretty semi precious gemstone Montana Agate comes from near the Yellowstone River...

    $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. Pretty semi precious gemstone Montana Agate comes from near the Yellowstone River in...

    $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 3 piece Set Suite Cabochons #16 Montana Agate 3 piece Set Suite Cabochons #16

    Montana Agate Cabochon Suite or Set #S16

    A 3 piece suite or set of beautiful dark brown and translucent semi precious gemstone Montana Agate designer cabochons. The middle stone cabochon is a trillion or triangle shaped cabochon with 19 mm long sides and the end stone cabochons are 41 mm...

    $120.00
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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. Pretty semi precious gemstone Montana Agate comes from near the...

    $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. Pretty semi precious gemstone Montana Agate comes from near the Yellowstone...

    $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. Pretty semi precious gemstone Montana Agate comes from near the...

    $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. Pretty semi precious gemstone Montana Agate comes from near the Yellowstone River in Montana...

    $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. Pretty semi precious gemstone Montana Agate comes from near the...

    $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. Pretty semi precious gemstone Montana Agate comes from near the Yellowstone River in Montana...

    $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. Pretty semi precious gemstone Montana Agate comes from near the Yellowstone River in Montana...

    $40.00
    Add to Cart
  • 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. Pretty semi precious gemstone Montana Agate comes from near the Yellowstone River in Montana...

    $36.00
    Add to Cart
  • 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. Pretty semi precious gemstone Montana Agate comes from near the Yellowstone River in...

    $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. Pretty semi precious gemstone Montana Agate comes from near the...

    $30.00
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  • Montana Agate Designer Cabochon Set Suite Semi Precious Gemstone #15 Montana Agate Designer Cabochon Set Suite Semi Precious Gemstone #15

    Montana Agate Cabochon Suite or Set #S15

    A 3 piece suite or set of beautiful milky translucent semi precious gemstone Montana Agate designer cabochons with black polka dots. The middle stone cabochon is a trillion or triangle shaped cabochon with 19 mm long sides and the end stone...

    $100.00
    Sold
  • 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. Pretty semi precious gemstone Montana Agate comes from near the Yellowstone...

    $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. Pretty semi precious gemstone Montana Agate comes from near the Yellowstone River in...

    $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. Pretty semi precious stone Montana Agate comes from near the Yellowstone River in...

    $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. Pretty semi precious gemstone Montana Agate comes from near the Yellowstone River in...

    $36.00
    Add to Cart