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Posted by: Donald Kasper
This is provably false.
The Union Road Missouri agates of sedimentary source rock scan in infrared with shells of celadonite. Celadonite cannot form from weathering.
That site sits on a fault and was subjected to Western orogency volcanic ash deposition as its silica source.
Subsea volcanic eruptions do two things. First they dump ash into the sea. Second they cause a radiolaria bloom. Third the silica settles to the sea floor and the radiolarian bloom dies out and settles down as well. Then you get say, a Mookaite, found in 7 beds of volcanic ash with radiolaria in a bentonitc chert. So then smart PhD's conclude radiolaria make agate and chert. No. Ash makes the agate and chert and radiolaria.
The Keokuk Geodes are not sedimentary. They are found under a bentonite bed with radiolara in the shells and kaolinite.
The Lake Magadii, Kenya chert, presumed to form by magadiite, is found by drill core under 45 feet of volcanic ash and 100 feet under the magadiite.
Magadii-type cherts from Rome, Oregon has crust shells of beta-moganite, bentonite, and celadonite. If I am correct in identifying beta-moganite in infrared, then they formed at or above 354 C. There are specific infrared reasons to make this presumption of moganite beyond discussion here, but my infrared has been calibrated in two blind studies to NASA Raman infrared from where moganite is defined. It is not defined by XRD, it is defined by what a Raman instrument says at 501 cm.
The sedimentary Dryhead agates are covered in celadonite and bentonite shells with the quartz/chert. You have to study the 4300 cm-1 phyllosilicate region in infrared to see it, or you just won't find it.