GeneralGeochemical Reactions for Agate, Jasper, Opal, Chert Formation
Here is my list that I last updated in this format in 2015 that covers 68 major pathways that are candidates for these silica rocks being formed. It is posted as a PDF file at donaldkasper dot com to download. The two pages are screen captured as pictures and listed here. This gives an idea of the vast geochemical world beyond a concept of weathering that I find relates to agate systems and their cohosted silica rocks. The document also lists the mechanisms I consider invalid in their formation. Western U.S. volcanics of much younger age than Permian European volcanics, still retains a vast archive of agate geologic systems, not seen any more on the European continent, most presumable long eroded away. Enjoy.
I find this subject very interesting. By chance, Donald, have you ever read of the research and experiments by Len Cram in Australia regarding the growth of opal? It goes against most traditional theories but I have become a believer in his research. I once had a glass jar that had been full of opals. The water had become dirty, so i took the opals out but kept the liquid in it. Therein started growing mini crystals floating in the water what I thought might be cristobalite. Somehow the jar cracked and water leaked out, but after years in a bottom shelf a thin coating of what looks like iridescent opal had grown on the inside of the jar. I also have a jar of mexican opals that has been leaking and growing crystals. I always thought perhaps that sulfur was the problem with the instability of virgin valley opal, and have done many experiments myself, but am now more inclined to say that manganese has something to do with it, along with other things I am still researching. I once saw a liquid opal in the wet clay in Virgin Valley, still gelatinous. It dried and cracked to powder very quickly. There is always more to learn than we already know. thank you for sharing this.
