Is there much, if any, spoilage that takes place when precious metals are melted?

SanctionII

For example molten silver or gold splattering on the smelter room floor during the process and/or residue in the smelter pot hardening during lulls in smelter operation which flakes off or chips off.

I assume that any such spoilage is retrieved with meticulous attention to detail and is placed back into the smelter.

cladking

Most people would be surprised how little gold is lost. Even the slag
is carefully processed along with everything else that it touches.

Silver ois not so tightly controlled because it's so much less valuable
but most smelting operations will lose well under .01%. Even silver
processes will usually have less than 5% wastage.

jonathanb

Yesterday I posted a thread with an account of a Contemporary (1872) argument for creation of Trade Dollar. Conveniently, one of the other pamphlets bound with that one has an exact answer to your question, at least as of 1872.

In Report upon the Wastage of Silver Bullion in the Melter and Refiner's Department of the Mint of the United States (Government Printing Office, Washington: July 25, 1872), it is reported that the "official statement of the melter and refiner's (Philadelphia Mint) last annual settlement exhibits the following details":

GOLD
337,892.269 ounces -- Total amount operated upon
337,807.224 ounces -- Redelivered to the treasurer
85.045 ounces -- Wastage

SILVER
3,430,953.99 ounces -- Total amount operated on
3,423,144.19 ounces -- Redelivered to the treasurer
7,809.90 ounces -- Wastage

...so my math says there was wastage of 0.025% (1 part in 4,000) for gold and 0.25% (1 part in 400) for silver. That was back in 1872. Techniques are presumably even better now.

They also found that surface contamination on refined bars was in the range of 0.1-0.3%.

The surface impurities on "strips and clippings remaining from the punching of dollar planchets...which were of an uniform dark color" came to 0.07%. They note that "Since the selection made for the above examination was of strips and clippings more than usually colored, it is fair to assume that the loss, here indicated, is a little above the average amount. Upon a careful inspection of large quantities of clippings, such as pass from the chief coiner to the melter and refiner, it is believed that 5/10 of 1/1000 represents a just average of the loss by surface impurities. Thus, on every thousand (1,000) ounces of silver clippings, a loss occurs of five-tenths (5/10) of an ounce; on one hundred thousand (100,000) ounces, a loss of fifty (50) ounces."

The pamphlet also goes on to discuss ALL costs related to refining and melting. For example, in the fiscal year 1871-1872, the Mint paid $1,858.86 for charcoal.

I have a pdf file that I can send to anyone who PMs me their email address. Total file size will be about 5 megabytes; make sure your email system won't choke on something that large.

jonathan

JupitarCoins

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