Deleted
Deleted Member
Member since January 1970
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Post by Deleted on Jan 31, 2016 19:48:25 GMT -5
T-eggs and amygdules form much differently. The former are gas pocket nodules that are usually found in basalt or andesite. Agate/chalcedony infills an often roughly almond shaped void in the host rock. Amygdules do not have the classic t-egg matrix shell. Too much typing to do T-egg ( lithophysae) formation but you can Google lots of explanations. Basically ( a way too simple explanation) t-eggs differ in that the star shaped gas pocket forms inside the matrix "shell" before infilling with chalcedony and the host rock tends to be an ash/perlite type deposit....Mel What is your opinion on whether they (either or both) may be the source of this gravel? Rather than seams and larger deposits?
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Sabre52
Cave Dweller
Me and my gal, Rosie
Member since August 2005
Posts: 20,466
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Post by Sabre52 on Jan 31, 2016 21:04:23 GMT -5
It looks to me like the agates are moss, plume and fortification amygdules in origin but vein hunks could tumbled down to resemble nodules too, as could agate wood casts. The pet wood or course, is obvious and expected and appears much like the selection you'd find in the George West area. There are T-eggs in west Texas but they don't contain that kind of interiors...Mel
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Post by socalagatehound on Jan 31, 2016 22:19:42 GMT -5
Hi guys Thought I would add to this if I may. A good reference work is "The Formation of Thundereggs (Lithophyse)" by Paul Colburn aka The Geode Kid. Its an excellent study with lots of scientific data and draws many logical conclusions. Paul dug tens of thousands of thundereggs and Geodes all over the U.S. and owned claims in several states. His lifetime collection is on display at the Lunes Mimbres Museum in Deming, New Mexico. Worth a stop if you're in the area or passing through. One of the things I can say from personal digging experience (dug a few thousand myself) is that the Lithophyse found in ash (degraded perlite) deposits, such as the Hauser Beds, Black Agate beds, etc, are not necessarily formed directly in the perlite, but rot (for lack of a better word) out of the rhyolite layers and settle into the ash layers. Through geologic action, they sink into the ash, sometimes into large groupings that unfortunately sink to the bottom of the ash over time. I have found "nests" of over 100 geodes at the Hauser Beds 6-12 feet down, but that was 10-12 years ago. Can't find 'em like that now. Amygdules can form in the same environment, sometimes in the same rock. I think the difference may be more about gas and silica content, temperature and moisture content of the rock during cooling and when the filling of the gas pockets occurred. Because the Texas agates are right in line with the large volcanic rift zone that runs from New Mexico thru Northern Mexico, I would think that they formed along that seam in pretty much every way possible and it is reflected in the stunning variety in what can be found. I think Mel nailed it that the agates have traveled a fair distance, but there are lots of areas in West Texas where similar stuff is found. On a totally differnet side note, on a trip some years ago to the Lucky Strike mine in Oregon, Kop and I opened a thunderegg filled with layers of silica pudding, agate that had not yet hardened. Cool experience.
Craig
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carloscinco
fully equipped rock polisher
Member since July 2008
Posts: 1,639
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Post by carloscinco on Feb 16, 2016 20:41:59 GMT -5
That's one beautiful set of river rocks. Mighty pleasing.
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