period - Author's Note.), although there is no certain reference to it in the description of the objects. The reddish-brown colour gives the test for iron, silver and copper, and is evidently due to iron and copper in the gold that have oxidized. In some instances a red or purple colour proved to be a staining of the gold by organic matter, since it was not soluble either in acids or in organic solvents, but could readily be removed by heating. The rose colour can be proved by chemical analysis not to be due to any colloidal modification of the gold, nor to any sort of organic lacquer or varnish, and the gold can be made red-hot without the colour being removed or diminished, but in some instances rather enhanced. The coloured film, however, is so extremely thin, being probably less than one hundred-thousandth of an inch in thickness, that without more material than it is advisable to use, chemical analysis becomes very difficult. A trace of iron is the only metal found so far, and since it is well known that native gold is sometimes reddened by being coated with a translucent film of oxide of iron, it is suggested that the colour in

(August 30, 2008)

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