archean/proterozoic barrier.
The term "visible life" refers to multicellular from before people knew there was life in the proterozoic.
This period is similar to the Quaternary, but it also includes tool usage by close relatives of humans which were not humans yet.
It ends together with the pleistocene.
Agriculture is not the official definition of the age. But it is good enough. Likely related to the official end of glaciations thing.
Made up mostly of calcium carbonate.
"Joachimsthal" is the German for it. Note how it is just near the modern frontier between Germany and the Czech Republic.
en.wikipedia.org/w/index.php?title=Uranium&oldid=1243907294#Pre-discovery_use:
In the early 19th century, the world's only known sources of uranium ore were these mines.
Apparently the region was a silver mining center:
Starting in the late Middle Ages, pitchblende was extracted from the Habsburg silver mines in Joachimsthal, Bohemia (now Jáchymov in the Czech Republic), and was used as a coloring agent in the local glassmaking industry
Falun mine tour by Focus by Sohaib
. Source. Not English, but we can see the tour images at least. Articles by others on the same topic
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