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Post by Admin on Jan 22, 2022 13:07:57 GMT -7
I like to TRY to decipher the past history of rocks like this one from the Wah Wah Mountains of western Beaver County Utah where there has been lots of volcanic activity. What came first?
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Post by Admin on Jan 22, 2022 13:09:05 GMT -7
It is usually obvious if a stone grew from the center out, like a pearl, or from the exterior to the center as in "fortification agate, or from the bottom up as in "waterline agate." Some of our understanding is clouded by "Old Scientist Tales." Here is another puzzle in Morrisonite, NOT my slabs. Note something different happened to the bottom two examples from the shattered examples on top. All examples were taken from Googling "Morrisonite Images."
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Post by Admin on Jan 22, 2022 13:09:20 GMT -7
It is snowing here! I took this photo indoors with a veg oil coating. Is that better Scott? Dave
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Post by Admin on Jan 22, 2022 13:11:33 GMT -7
Luckily we have the Bruno Jasper to help us understand what happened to some Morrisonite. Bruno began as spheroids that were "popped open" by water expanding up to 2,000% into steam as cooling and contracting magma reduced the surrounding pressure. As cooling continued, the openings became vacuum chambers. In other areas the spaces were produced by openings in ledge rock. in both cases, the chambers were surrounded by highly silicious clay. Blobs of that material was injected into the chambers by repeated pulses by something like Old Faithful repeatedly pressurizing the groundwater.
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Post by Admin on Jan 22, 2022 13:12:35 GMT -7
How do the plumes and moss form? I just visited my saw shop where it is cold now. Here is my bottle of Dawn! You folks from the warm wild coast could put your bottle in the frig and think thank thunk upon the phenomenon.
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Post by Admin on Jan 22, 2022 14:06:47 GMT -7
Here are some fill sequences to examine from Brazilian Amygduloids. a closer look: Another: And my favorite:
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Post by Admin on Jan 22, 2022 14:08:11 GMT -7
I found the first example intriguing in that at one time quartz crystals grew, then the fluids heated up and melted the terminations, then the smoky cloud material entered. Far easier to interpret are planar layers that built from the bottom up. The sequences are easily verified by the "Tilt Egg" (a photo of this specimen was the picture of the day on Mindat.org back in June '13) that obviously filled, the dried out, the rock shifted slowly down on one side, repeated numerous times.
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Post by Admin on Jan 22, 2022 14:09:26 GMT -7
Dave, had you ever seen a geode with stalactites before? The progression of that formation is pretty amazing. Jim Yes, These were later coated with quartz crystals. The Geode Kid calls them "Angel Wings." Stalactites grew in many rock cavities, then were embedded in new material before we came on the scene to enjoy them. We find them in slices from time to time. Most folks call hollow thundereggs duds. I find them very informative! There are boulders full of them around Richardson Ranch, Madras Oregon. They must have been above the water table when the fill sequences began.
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Post by Admin on Jan 22, 2022 14:11:12 GMT -7
This specimen shows it's spheroid ancestry better than most, and the interrupted fill sequence allows easier investigation into what has happened to this point.
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Post by Admin on Jan 22, 2022 14:17:29 GMT -7
I like "reading" rocks. These started as gas bubbles in basalt with a lot of froth around them. A lot of calcite in first fills. A fracture through one of them later sealed. Most interesting!
And this one! What an entertaining novel with hours of pleasurable reading! Starts with an empty gas bubble followed by a HOT fortification outer shell followed by millennia of quiet waterline fills, then the story heats up as fortification agate builds up again. Some bubble blebs, hot and cool repeats, Shifts in color minerals, crystallization and a cavern ending.
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