This invention relates to quaternary gold alloys, and more particularly, to gold-silver-copper-zinc alloys generally designated as 8 to 12-carat gold alloys.
Gold is a valuable metal and is used ornamentally in the form of necklaces, pendants, rings or the like. For ornament use, pure gold or so-called 24-carat gold can be easily worked, but is susceptible to damage because it is relatively soft. For this reason, 14 to 18-carat gold alloys are generally used for ornaments.
As is publicly known, 18-carat gold alloys are those containing 18 parts by weight of pure gold per 24 parts by weight of the entire alloy. That is, the 18-carat gold alloys contain 75% by weight of pure gold. The 14-carat gold alloys contain 58.3% by weight of pure gold. The remainder, for example 25% in the case of 18 carats, consists of alloying components which are usually silver and copper. More particularly, silver and copper are incorporated at a relative weight ratio of 6:4 to 5:5 into gold alloys. Such gold alloys must have not only golden color tone and luster, but also improved hardness and abrasion resistance.
In the gold ornament industry, 14-carat gold is believed to be the minimum level to work into a workpiece having satisfactory golden color tone and luster.
Prior art gold alloys of 9 to 10 carats are less attractive in color tone. Those alloys containing copper and silver in a weight ratio of 8:2 are reddish gold and those containing copper and silver in a ratio of 7:3 are slightly reddish gold although they are easy to work. Since they are susceptible to oxidation, they turn more reddish as time goes by. In general, articles of 9 to 10 carats are futher plated with 18 carat or more gold alloys or pure gold to compensate for the lack of color tone and oxidation resistance.