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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 Translucent Cabochons Stones #3 Montana Agate Matched Pairs Translucent Cabochons Stones #3

    Montana Agate Matched Pair Cabochons #3

    Triangle shaped matched pair milky translucent with black spots semi precious gemstone Montana Agate designer cabochons 32 mm by 10 mm and 4 mm thick. These weigh about 7 carats each. Pretty semi precious gemstone Montana Agate comes from...

    $48.00
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  • Montana Agate Translucent Long Triangle Cabochon Stone #21 Montana Agate Translucent Long Triangle Cabochon Stone #21

    Montana Agate Cabochon #21

    Long triangle shaped milky translucent with black spots semiprecious gemstone Montana Agate designer cabochon 46 mm by 9 mm and 3 mm thick. Pretty semi precious gemstone Montana Agate comes from near the Yellowstone River in Montana. In Montana...

    $20.00
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  • Montana Agate Translucent Polka Dot Triangle Cabochon Stone #20 Montana Agate Translucent Polka Dot Triangle Cabochon Stone #20

    Montana Agate Cabochon #20

    Small triangle shaped milky translucent with black spots semiprecious gemstone Montana Agate designer cabochon 27 mm by 7 mm and 4 mm thick. Pretty semi precious gemstone Montana Agate comes from near the Yellowstone River in Montana. In Montana...

    $10.00
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  • Montana Agate Polka Dot Small Triangle Cabochon Stone #19 Montana Agate Polka Dot Small Triangle Cabochon Stone #19

    Montana Agate Cabochon #19

    Small triangle shaped milky translucent with black spots semiprecious gemstone Montana Agate designer cabochon 19 mm by 15 mm and 4 mm thick. Pretty semi precious gemstone Montana Agate comes from near the Yellowstone River in Montana. In Montana...

    $10.00
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  • Montana Agate Translucent Small Cabochon Jewelry Stone #5 Montana Agate Translucent Small Cabochon Jewelry Stone #5

    Montana Agate Cabochon #5

    Tiny trapezoid shaped milky translucent with black spots semiprecious gemstone Montana Agate designer cabochon 18 mm by 4 to 7 mm and 3.5 mm thick. Pretty semi precious gemstone Montana Agate comes from near the Yellowstone River in Montana...

    $8.00
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  • Montana Agate Translucent Small Triangle Cabochon Jewelry Stone #18 Montana Agate Translucent Small Triangle Cabochon Jewelry Stone #18

    Montana Agate Cabochon #18

    Tiny triangle shaped milky translucent with black spots semiprecious gemstone Montana Agate designer cabochon 19 mm by 5 mm and 3 mm thick. Pretty semi precious gemstone Montana Agate comes from near the Yellowstone River in Montana. In Montana...

    $8.00
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  • Montana Moss Agate Translucent Small Triangle Cabochon Stone #15 Montana Moss Agate Translucent Small Triangle Cabochon Stone #15

    Montana Agate Cabochon #15

    Tiny triangle shaped milky translucent with black spots semiprecious gemstone Montana Agate designer cabochon 16 mm by 9 mm and 3 mm thick. Pretty semi precious gemstone Montana Agate comes from near the Yellowstone River in Montana. In Montana...

    $8.00
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  • Montana Agate Translucent Small Triangle 8 mm Cabochon Stone #1 Montana Agate Translucent Small Triangle 8 mm Cabochon Stone #1

    Montana Agate Cabochon #1

    Very tiny triangle shaped milky translucent with black spots semiprecious gemstone Montana Agate designer cabochon about 8 mm and 4 mm thick. Pretty semi precious gemstone Montana Agate comes from near the Yellowstone River in Montana. In Montana...

    $6.00
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  • Montana Agate Matched Pair Triangle Designer Cabochons #5 Montana Agate Matched Pair Triangle Designer Cabochons #5

    Montana Agate Matched Pair Cabochons #5

    Triangle shaped matched pair milky translucent with black semi precious gemstone Montana Agate designer cabochons 26 mm by 9 mm and 3.5 mm thick. These weigh about 4 carats each. Pretty semi precious gemstone Montana Agate comes from near the...

    $36.00
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  • Montana Agate Matched Pairs Loose Stones Cabochons #7 Montana Agate Matched Pairs Loose Stones Cabochons #7

    Montana Agate Matched Pair Cabochons #9

    Trapezoid shaped matched pair milky translucent with black polka dots semi precious gemstone Montana Agate designer cabochons 17 mm long by 4 to 8.5 mm wide and 3.5 mm thick. These weigh about 3.5 carats each. Pretty semi precious gemstone...

    $20.00
    Sold
  • Montana Agate Small Moss Matched Pair Cabochons Designer #14 Montana Agate Small Moss Matched Pair Cabochons Designer #14

    Montana Agate Matched Pair Cabochons #14

    Short trapezoid shaped matched pair milky translucent with black semi precious gemstone Montana Agate designer cabochons 7 mm by 3 to 9 mm wide and 3.5 mm thick. These weigh about 4.5 carats each. Pretty semi precious gemstone Montana Agate...

    $20.00
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  • Montana Agate Translucent Small Triangle Cabochon Stone #11 Montana Agate Translucent Small Triangle Cabochon Stone #11

    Montana Agate Cabochon #11

    Small triangle shaped milky translucent with black spots semiprecious gemstone Montana Agate designer cabochon 19 mm on 2 sides by 18.5 mm on the third side and 4 mm thick. Pretty semi precious gemstone Montana Agate comes from near the Yellowstone...

    $10.00
    Sold
  • Montana Agate Translucent Small Triangle Cabochon Stone #10 Montana Agate Translucent Small Triangle Cabochon Stone #10

    Montana Agate Cabochon #10

    Tiny triangle shaped milky translucent with black spots semiprecious gemstone Montana Agate designer cabochon 19 mm by 9 mm and 4 mm thick. Pretty semi precious gemstone Montana Agate comes from near the Yellowstone River in Montana. In Montana...

    $10.00
    Add to Cart
  • Montana Agate Matched Pairs Polka Dotted Cabochons Stones #18 Montana Agate Matched Pairs Polka Dotted Cabochons Stones #18

    Montana Agate Matched Pair Cabochons #18

    Triangle shaped matched pair milky translucent with black and brown spots semi precious gemstone Montana Agate designer cabochons 24 mm by 9 mm and 4 mm thick. These weigh about 6.5 carats each. Pretty semi precious gemstone Montana Agate...

    $36.00
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  • Montana Agate Matched Pair Cabochons Trapezoids #17 Montana Agate Matched Pair Cabochons Trapezoids #17

    Montana Agate Matched Pair Cabochons #17

    Trapezoid shaped matched pair milky translucent with black polka dots semi precious gemstone Montana Agate designer cabochons 18 mm long by 4 to 9.5 mm wide and 3.5 mm thick. These weigh about 4 carats each. Pretty semi precious gemstone...

    $30.00
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  • Montana Agate Matched Pair Trapezoid Jewelry Designer Cabochons #23 Montana Agate Matched Pair Trapezoid Jewelry Designer Cabochons #23

    Montana Agate Matched Pair Cabochons #23

    Trapezoid shaped matched pair milky translucent with black semi precious gemstone Montana Agate designer cabochons 22 mm by 3.5 to 8 mm and 4 mm thick. These weigh about 4.5 carats each. Pretty semi precious gemstone Montana Agate comes from near...

    $36.00
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  • Montana Agate Matched Pairs Transparent Cabochons Stones #8 Montana Agate Matched Pairs Transparent Cabochons Stones #8

    Montana Agate Matched Pair Cabochons #8

    Triangle shaped matched pair milky translucent with black and brown spots semi precious gemstone Montana Agate designer cabochons 29 mm by 11 mm and 4 mm thick. These weigh about 6.5 carats each. Pretty semi precious gemstone Montana Agate...

    $40.00
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  • Montana Agate Translucent Spots Triangle Cabochon Stone #8 Montana Agate Translucent Spots Triangle Cabochon Stone #8

    Montana Agate Cabochon #8

    Triangle shaped milky translucent with black spots semiprecious gemstone Montana Agate designer cabochon 33 mm by 16 mm and 4 mm thick. Pretty semi precious gemstone Montana Agate comes from near the Yellowstone River in Montana. In Montana Agate...

    $24.00
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  • Montana Agate Matched Pairs Triangles Cabochons Stones #13 Montana Agate Matched Pairs Triangles Cabochons Stones #13

    Montana Agate Matched Pair Cabochons #13

    Triangle shaped matched pair milky translucent with black and brown spots semi precious gemstone Montana Agate designer cabochons 33 mm by 10 mm and 4 mm thick. These weigh about 6.5 carats each. Pretty semi precious gemstone Montana Agate...

    $40.00
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  • Montana Agate Matched Pairs Translucent Cabochons Stones #20 Montana Agate Matched Pairs Translucent Cabochons Stones #20

    Montana Agate Matched Pair Cabochons #20

    Triangle shaped matched pair milky translucent with black and brown spots semi precious gemstone Montana Agate designer cabochons 33 mm by 11 mm and 4 mm thick. These weigh about 7 carats each. Pretty semi precious gemstone Montana Agate...

    $40.00
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  • Montana Agate Matched Pairs Designer Cabochons Stones #16 Montana Agate Matched Pairs Designer 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...

    $20.00
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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 Long Triangles #22 Montana Agate Matched Pair Cabochons High Grade Long Triangles #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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