bumblebee Posted March 31, 2022 Report Share Posted March 31, 2022 It took this article to inspire me to bang two handmade agates together in the dark. I was quite delighted by the repeatable results: an orange spark. Apparently on the massive red sandstone grinding wheels of Idar-Oberstein, due to the intense speed and friction, this sparking becomes something of a fireworks show as the agates "become throughout splendidly luminous with red light and at the same time transparent." 1874-The-Philosophical-Magazine-Light-In-The-Grinding-Stones.pdf 2 Link to comment Share on other sites More sharing options...
Steph Posted March 31, 2022 Report Share Posted March 31, 2022 Interesting ... that you did it. And that this 79-year-old man thought it was interesting enough to study and write an article about and encourage further study of. Link to comment Share on other sites More sharing options...
Ric Posted April 2, 2022 Report Share Posted April 2, 2022 His description of cracking and fragmenting grinding stones is pretty harrowing. I hadn't thought about that before but I sure wouldn't want to anywhere around when it happened - yikes! 2 Link to comment Share on other sites More sharing options...
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