Want to do a group excercise?
I found this rock years ago in the Ambitzgi Riet which you can find on Maps at (47°18'10.5"N 8°48'23.9"E). It is a swampy area dominated by drumlins and anthropogenic interferences such as a railway line, where people go to take a walk and stuff. Back then I went to an alpine petrologist at ETH Zürich to ask their opinion on it, as I myself wasn't quite sure what to make of this rock after trying to determine it on my own. It does not react with hydrochloric acid, except for on one of the edges (you can probably already see which one). Overall it has rough edges & cuts, except for one area in which it is more eroded & smoothened. Most of it has a matte shine, except for almost all of the fillings in those round sorta dots. Some of those fillings are transparent, some aren't & just white. The dots /balls may be a filling. We didn't do a chemical analasys back then & I didn't go a second time with the same rock. Back then the answer was it's probably chalcedon and agate /achat. You can find rock like this in Germany or more likely even Mexico, thing is: Not in the swampy area I found it at and not anywhere adjacent to it. So here's the question: He was probably correct on the composition of the rock, though it may contain more stuff that went unmentioned. If we can assume all of it was correctly stated, what do you believe to be the story behind how it got to where I found it? What would you challenge or check again?