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Post by rmf on Jan 30, 2018 9:36:39 GMT -5
It may be cool now but it was hot before.
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Deleted
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Post by Deleted on Jan 30, 2018 12:47:00 GMT -5
That makes a very nice specimen that illustrates how agates/chalcedony, opal and other materials form in cavities within vesicular basalt and similar (as opposed to seams or flows). Your piece also is an example of how one chamber can often be completely filled, surrounded by other voids in which there isn't even a trace of filling. Since there is usually no detectable point of entry for the material, it makes for a little geological puzzle.
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fvpty
noticing nice landscape pebbles
Member since July 2017
Posts: 95 
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Post by fvpty on Jan 30, 2018 13:31:52 GMT -5
That makes a very nice specimen that illustrates how agates/chalcedony, opal and other materials form in cavities within vesicular basalt and similar (as opposed to seams or flows). Your piece also is an example of how one chamber can often be completely filled, surrounded by other voids in which there isn't even a trace of filling. Since there is usually no detectable point of entry for the material, it makes for a little geological puzzle. It do have some small geodes will up load some pic’s its a relley nice specimen that trully explain the process of all ... thanks for your ping point comments 👍🏻 |
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Sabre52
Cave Dweller 
Me and my gal, Rosie
Member since August 2005
Posts: 20,497
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Post by Sabre52 on Jan 30, 2018 19:16:18 GMT -5
Yeah,I was also gonna say how, at the Woodward Ranch here in Texas, the plume biscuits form in vesicles just like that. There was one cliff we came across where the basalt showed dozens of embedded agates in cross section where the cliff had sheared away and sheared off the nodules at the same time. One of the agate books, maybe Zenz's has a picture explanation of how those nodules fill. Very interesting!.....Mel
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Post by HankRocks on Jan 30, 2018 20:24:07 GMT -5
After spending a lot of hours at Walker Ranch, Marfa Agate fields and the Agate locations around Lajitas, my own theory suggests that the material that creates the agate forms into the "bubbles" as the igneous mass is still in semi-liquid(if that's the right description). All of the non Basalt and Rhyolite separating out into bubbles, or if enough, veins. As the mass begins to cool different minerals crystalize at each's respective temp, quartz or micro-crystaline quartz being last. Some of the pockets form voids that allow the Quartz to form into bigger crystals. In some cases the bubbles are empty, air pockets which is probably related to some formation constraint. It all has to do with the mixture of the flow.
There are some neat formations about a half mile due north of Lajitas with Basalt columns. Some exposed columns can rise 70 or 80 feet above the wash. On top of the Basalt columns there is a Rhyolite cap, 4 to 6 foot in depth and that cap is where the Geodes and agate nodules formed. Most of the geodes are flattened and some up to 2 foot in diameter. There is no agate in the Basalt, and that might make sense as the Basalt was pure enough to crystalize, along with proper cooling.
Just my observations.
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Post by fernwood on Jan 30, 2018 21:01:30 GMT -5
A very nice find and excellent geological example of how some beautiful rocks in general were formed. Extreme conditions and the passing of time with other geological conditions create some amazing specimens. Thanks for sharing.
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fvpty
noticing nice landscape pebbles
Member since July 2017
Posts: 95
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Post by fvpty on Jan 31, 2018 8:11:20 GMT -5
That makes a very nice specimen that illustrates how agates/chalcedony, opal and other materials form in cavities within vesicular basalt and similar (as opposed to seams or flows). Your piece also is an example of how one chamber can often be completely filled, surrounded by other voids in which there isn't even a trace of filling. Since there is usually no detectable point of entry for the material, it makes for a little geological puzzle. It do have some small geodes will up load some pic’s its a relley nice specimen that trully explain the process of all ... thanks for your ping point comments 👍🏻 Here are some pic’s for more detail of the specimen... the cube is a cut from a near pice of the large stone . Apears to have little bubbles but when you magnify yo see they are all micro geodes here are the pics from the specimen and the pics from the small cut pieces taking out the specimen from matrix ....       |
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fvpty
noticing nice landscape pebbles
Member since July 2017
Posts: 95
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Post by fvpty on Feb 1, 2018 21:13:35 GMT -5
Thanks guy’s for all your comments keep on rocking ! 💪🏻⚒
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Post by fernwood on Feb 3, 2018 6:48:12 GMT -5
Cool cube.
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