One of the guests on the BBC's In Our Time episode on the California Gold Rush claimed that the gold coming out of California mines increased the supply of gold coins in the United State twenty times. Further, he claimed that there was a mint in San Francisco by 1860. These mines were private claims, so how did the gold flakes and nuggets they pulled from the rivers of northern California become coins? Did the government purchase the ore, mint the coins, and then issue them in fashion? Did private banks commission the mints to convert gold they purchased into US currency?
This also involves the Carson City federal mint in Nevada (drawing on the famed Comstock Lode), established in 1869. These mints purchased bullion, either directly from major mines or from banks, which purchased bullion from the market (including from smaller producers). Although the mints were capable of refining the bullion, they often acquired precious metal that required nothing or little more than assay work to make certain the bullion met the purity standard required for a US coin. The rest is a matter of transforming ingots into round blanks, which is merely an industrial process involving heat, rollers, and cutting followed by the actual stamping of the mint press.
I know exactly the book you want:
From Mine to Mint, by Roger W. Burdette, is the work of a focused enthusiast that examines the functional design and manufacture of American coinage. This 500 page tome focuses on the period 1833-1937, and is targeted chiefly at collectors and numismatists. It does not contextualize it's findings but does describe the internal workings of the U.S. Mint, as well as it's manufacturing technology, in exquisite detail. A reasonable summary and review (although decidedly non-academic in tone) can be found here: http://www.coinbooks.org/esylum_v16n12a04.html