Hi, I'm jumping in from the SFI thread -
I found those balls at a mine which was in operation ~mid 20th century, and it was not an iron mine. They are just an example of a type of crushing technology which is used for many different mining and processing applications, not limited to ore type or a particular century.
I'm not sure how far back the use of ball mills for ore processing goes in the Mojave, probably to the mid 19th (when it all started there), but it continues to this day, and I think they are more commonly post-industrial tech.
Most of the early mining activity in the American SW was probably wiped out by later, more industrial efforts, there are some pretty huge iron mines from the early - mid 20th C. out there.
Edit - I checked Biringuccio's Pirotechnia to see what miners were using in the 16th C, and he's pretty vague, lots of mentions of milling things, but I didn't see much description of the mills - he mentions stamp mills & flour-type mills.
I recall some reference to the Spanish mines in California crushing ore or mixing with mercury using a stone wheel that rolls around in a circle, but can't find the specific book.
Jeff
Last edited by Jeff Pringle; 2nd November 2005 at 02:27 PM.
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