In this article we will focus on the most popular precious metals used for jewelry: gold, Precious metals in jewelry manufacturing and their best use Articles platinum and the fast growing in popularity palladium.
Pure gold and platinum are soft metals which are extremely dense. pure gold is about two and half times heavier than iron and pure platinum is just under three times. While really bright in color pure metals are not suitable for fine jewelry because of their softness. Soft metals are easy to damage, difficult to polish, and unsuitable for detailed work. This is why they are mixed (alloyed) with other metals, in order to give them the desired properties. This is also where all this “carats” and confusing numbers come into play. In fact it is pretty simple:
All pure metals in nature are white or gray in color except two, gold – bright yellow and copper- reddish pink. Now we go back to precious metals.
All different colors of precious metals are achieved by mixing these colored metals with white ones.
Carat is a confusing name for purity or fineness of precious metals. It is confusing because the same word is used as a weight measurement for precious stones. That carat is equal to 0.2gr. and have nothing to do with metal fineness. To differentiate the one carat from the other, in some standards, weight carat is marked with ct and purity karat with kt or k. We can accept this rule to avoid confusion in further articles, therefore when we address metal purity we will use “karat”. Karat is used mainly to define purity of gold alloys. Different countries have different standards for gold purity and the most used globally alloys are: 9kt or 375, 10kt or 416, 14kt or 585, 18kt or 750, 21kt or 875 and 22 or 916. The alternative number which alone can be used as hallmark indicates the number of fine gold parts in the alloy out of 1000. The easy way to translate this into a manageable information is to perceive it as the percentage of fine gold used x10. For example 750 means 75% pure gold content or 18kt.Platinum is used in almost pure form and 95% hallmarked 950 is a standard alloy. All alloys with pure platinum content of 95.0% or higher can be also marked with the full word “platinum” or “”plat.” Other used alloys are 900 (90%), 800 (80%) and 585(58.5) also called karat platinum. The amazing qualities of this metal are better described in another article where I am comparing it with the white gold alternative.Palladium 950 alloys are as white as the platinum, blending well with white diamonds and eliminating the need of rhodium plating. Palladium is a light metal with weight close to the one of sterling silver and much lighter than platinum and high carat gold alloys, thus making it the metal of choice for items like large earrings. At the time of writing, the price of 950 palladium alloys is about a third of the price of the 18k white gold offering great possibilities for large solid pieces at significantly reduced price. One disadvantage though is that quality casting of palladium requires materials and equipment, currently not viable for small workshops.
The hallmarks you will usually find on your precious metal jewelry are:
1). Karat or fineness stamp (e.g. 18kt/ct or 750)
2) Manufacturer’s stamp
The karat stamp does not have much value without the manufacturers stamp because the declaration of purity is not signed. Beware; in most countries you can buy a karat stamp for few dollars.
Variety in gold colors and mechanical properties is achieved by alloying fine gold with one or more other metals. White gold for example is a gold alloy with whitening metals, usually palladium, nickel or silver or combination of them. Since the fine gold is always yellow, it is the alloy (base) metals that give the karat gold its color and properties. For example to be able to stamp an item as 18k it must content at least 75% of fine gold. The remaining 25 percent of alloy metals will determine its color and physical properties. If 8.4% of copper and 16.6% silver is used in the alloy, we will end up with the traditional rich 18k yellow gold color. If we mix the same amount of fine gold with 15 % of palladium and 10% of silver we will have good quality white gold. The constant content in 18k gold alloy is always 75% pure gold. Higher than 18k white gold alloys are not possible because the alloying metals are not in sufficient quantity to absorb the yellowness of the pure gold. 21k or 22k gold is always yellow, very yellow.