The Metals Used in Jewelry

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Gold has been used to make jewelry and many other treasured items since antiquity. Pure gold is referred to as 24 karat or fine gold. It is a deep yellow color. Fine gold is too soft to easily fabricate into jewelry and so jewelers alloy it with other metals to make it strong and workable. In yellow gold the most common alloys are copper, tin, silver and zinc. Nickel is alloyed with pure gold to make white gold.

The purity of gold is expressed in Karats. The karat stamp a consumer finds on a piece of jewelry is a number that indicates the amount of pure gold used. For example, 14k means 14 parts pure gold and 10 parts alloy. The remainder of the formula, as shown below, is an unstated number but represents the amount of the alloy used. The sum of this formula always adds up to 24. The following chart shows the ratios of pure gold to alloy in commonly used karat gold jewelry.

Platinum is another of the precious metals used in jewelry. It was first discovered by the Spanish in South America. Although they thought they had discovered Silver, it was later determined to be a different metal altogether. It is worth noting that the Spanish word for Silver is Platina. When used in jewelry, the purity of platinum is stated in percentages and actually refers to the alloy content. Two of the metals most commonly alloyed with pure platinum are iridium or ruthenium, although cobalt has recently been alloyed with platinum for use in jewelry. The amount of alloy most often used is 10%. So a stamp in a platinum jewelry would read “10% Irid. Plat” or “10% Ruth. Plat.”

Platinum was widely used in diamond jewelry prior to World War II. But at the outbreak of World War II, Platinum was declared a strategic metal, and so White gold was developed by the jewelry industry to replace Platinum. The differences between Platinum and white gold are significant. Platinum has a higher reflective index, which means it reflects a purer white light. Also platinum is more abrasive resistant than white gold and not prone to some of the chemical corrosion that sometimes effects white gold. Platinum jewelry is also more expensive than white gold. The reasons are these; Platinum is a denser metal than gold. That is to say that a piece of Platinum equal in size to a piece of gold will weigh more than the gold. Another factor is that alloys used to make karat gold are not as expensive as the pure gold itself. In Platinum however, the alloys are actually more expensive than the Platinum. And finally, on the commodities markets, Platinum is somewhat higher than pure gold in initial cost.

How gold can turn your skin black

To bring a fine gold down to a certain karatage, alloys of fine silver and copper are commonly used; and as we all know, silver tarnishes or turns black, when abraded or exposed to certain chemicals. Abrasion can result from dust, scouring compounds, talcum or even facial powders; anything containing chlorine, sulfur, or strong acids can be suspect on the chemicals side. In addition to chemicals in the environment, a person’s body chemistry can also be a cause. It’s not unusual to find that only one of several of a customer’s rings are affected by this problem, which can be attributed to differences in the silver content of the alloys of the rings. In cases where a household compound is applied and only one hand is used to scrub, only the rings on that hand may be affected. In chronic cases where the environmental causes discussed above can’t be identified, it’s recommended that 18k yellow gold be used, as it contains less silver.

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