The E-Sylum:  Volume 9, Number 31, July 30, 2006, Article 29

THOUGHTS ON BRITTLE GOLD

Professor of Chemistry Peter Gaspar writes: "The topic of brittle
gold introduced by Dick Hanscomb in the July 9th E-Sylum is
numismatically significant and has been discussed for more than a
century.  Unfortunately, the heat treatment recommended by Dick
Johnson may fail.

G. F. Ansell, in his "Royal Mint" 3rd edition, London, 1871
discusses brittle gold on pp. 49-53.  He blames the brittleness
on the annealing (softening by heating) before striking of gold
blanks which contained antimony, arsenic, and lead impurities.
Ansell claimed that such brittle gold could be converted into
perfectly sound coins, so long as the blanks were not annealed.
This is different from Hanscomb's brittle gold which cannot even
be rolled.  Ansell coined sovereigns in the London mint from brittle
gold in 1859, and they can be recognized by a line he placed on the
ribbon in Victoria's hair.  See Major Pridmore's "The Ansell Soverign"
in the Spink Numismatic Circular, November 1964, p. 258.

In "The Metallurgy of Gold" by T. K. Rose and W. A. C. Newman, 7th
edition, London, 1937, the most potent impurity leading to brittle
gold is said to be bismuth, and bismuth-embrittled gold is not softened
by heat treatment and must be refined.  The brittleness of gold caused
by tellurium increases with annealing, but softening occurs for other
impurities.  Since different samples of raw gold will differ in their
impurities, the variations in rolling and blanking observed by Dick
Hanscomb are consistent with what metallurgists have written about
gold alloys."

Ken Douglas agrees: "Dick Hanscom's problem with the gold may be a
purity problem. When I was young, I worked in a jewelry company as
a press operator. I carried a bar of gold around in my pocket while
I was working without thinking about its value. The gold scrap was
recycled many times and probably picked up impurities each time it
was melted. The results were what Hanscom described.

I am of the opinion that if he melts it, cleans off as much residue
as possible, lets it cool, and cuts it up for a remelt a couple of
times, he may get better results. This is just an opinion since I
did not have a direct hand in the melting and that was almost 50
years ago.  He might also cast his planchets rather than rolling
them."

  Wayne Homren, Editor

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