E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
King of Metals.
Gold, which is not only the most valuable of metals, but also is without its peer in freedom from alloy. It is got without smelting; wherever it exists it is visible to the eye; and it consorts with little else than pure silver. Even with this precious alloy, the pure metal ranges from sixty to ninety-nine per cent.