Gold, in its purest form, 24 Kt, is a very soft and pliable metal. The malleability, ductility, and softness of pure gold make it somewhat useless for wearing as jewelry. In order to make gold jewelry that is durable and long-lasting, it is combined with other metals called alloys. Jewelers use this combination with other metals such as silver, copper, and zinc, with the pure gold to make it harder and stronger; thus, giving it durability and wear resistance in day to day activities. In an attempt to achieve the best balance between the strength of alloys and the valuable and desirable properties of gold, three different karat gold combinations have become standard: 18Kt, 14Kt, and 10Kt. White gold alloys are typically stronger than yellow gold alloys.
18 Karat Gold
The content of 18Kt is 75% gold and 25% alloy. 18Kt gold is the softest and purest of these three karat golds, and it is also the most expensive because of its higher pure gold content. Higher-end jewelry where a richer yellow color is desired is typically made in 18Kt. It is the most resistant to the tarnishing of the three golds, and although it is the softest, it is still hard enough to be used for fine jewelry. 18Kt gold will show wear marks sooner and wear out slightly faster than 14Kt and 10Kt gold, but it is still the preferred choice of those wanting something finer.
14 Karat Gold
The content of 14Kt is 58.3% gold and 41.7% alloy. Due to the higher amount of alloy, 14Kt gold is therefore harder and stronger than 18Kt. It still has a good yellow color for those wanting fine jewelry at a more reasonable price.
10 Karat Gold
The content of 10Kt is 41.7% gold and 58.3% alloy. 10Kt is the only karat gold that contains more alloy than gold. It is the least pure, and therefore, the least expensive of the three gold contents. 10Kt gold is the preferred metal for class rings and other jewelry pieces where a lower cost is desired as well as worn daily. 10Kt yellow gold is slightly more pale in color and will tarnish more quickly than 18Kt and 14Kt gold jewelry. 10Kt gold is generally considered to be harder than 14Kt, but there is a much-unresolved discussion within the jewelry industry about whether or not it actually wears longer than 14Kt.
Many manufacturers are now using international gold marks to show the purity of their jewelry items. In these cases, the fineness of the precious metal content is expressed in parts-per-thousand. This marking system, universally recognized, is actually more accurate. We have listed the applicable marks here along with their corresponding karat marks:
24Kt = .999
18Kt = .750
14Kt = .585
10Kt = .41
Gold is a very yellow metal, and the color is influenced by the proportions and combinations of the other non-gold metals that are added as alloys.
Yellow gold is usually a mixture of silver and copper. As the purity content is higher the warmer the coloration.
White gold is not a true white metal like platinum, palladium, or silver. It is made by alloying pure yellow gold with other white metals like silver, zinc, and nickel to change its color to white. As a result, it always has a yellowish tint, and the darkness of that is also related to the purity factor.
To enhance the whiteness of white gold jewelry, it has become a standard practice in the jewelry industry to cover (or plate) with another precious metal called rhodium. Rhodium plating is very white, reflective, extremely hard, and virtually tarnish-free. However, rhodium coatings wear off gradually. It can be re-plated with rhodium, sometimes as often as within 1 year for rings worn every day, or as seldom as every 5 years. Still, many people prefer to wear white gold with the natural not-quite-white look of white gold, and don’t wish to deal with maintenance.
Rose or Pink Gold
These Karat golds are combined with high copper-content alloys and have similar properties. They were very popular in the latter half of the 19th century and the earlier part of the 20th century, and are now enjoying a resurgence in popularity. The high copper addition is usually at the expense of silver, giving a warm hue that compliments certain gemstones and skin tones.
Platinum is regarded as the preeminent metal for fine jewelry. It has a much higher content of the pure platinum and is one of the only metals that is hypoallergenic (ideal for those with sensitive skin). Platinum is also chemically inert, so it will not tarnish, corrode, oxidize or discolor. It is a strong, dense metal, and in same volume, weighs about twice the weight of 14Kt gold, and twenty-five percent heavier than 18Kt gold. This gives platinum jewelry its hefty feel!
All platinum jewelry is generally stamped with either PLAT, PT950, or 90 PLAT-10 IRID, both of which indicate 90-95% pure platinum and 5-10% alloys of either iridium, palladium, or ruthenium. Platinum is naturally white, very durable, and typically outlasts gold for many years.
Platinum is a rare metal that today requires the processing of nearly ten tons of ore for a single once of platinum. In comparison, Gold requires only three to four tons of raw rock for the same yield. There are also fewer platinum mines. For every ten Gold mines, there is one platinum mine. Platinum is known as the most prestigious jewelry material.
There is one other factor that should be considered when choosing a durable metal: prong wear. Unlike gold, which dents or breaks off when it is bumped up against something, platinum mashes down without breaking off, so it is vital in a prong-set or pave’, or today’s mini-prong style.
Palladium is also a platinum group metal. This metal group includes platinum, ruthenium, osmium, iridium, and rhodium. These metals are found together in nature and have similar qualities. They are rare, white in color, extremely durable, and unaffected by elements in the air that make other metals tarnish. As the market price of palladium has risen, it is rarely available as fine jewelry; many manufacturers are no longer offering palladium!
Palladium used for making jewelry products is typically 95% pure palladium and 5% of other platinum group metals such as iridium and ruthenium. The palladium alloys are white, hypo-allergenic, lightweight, and durable. These alloys have a specific gravity close to that of 14Kt white gold; so the weight by volume is about half the weight of platinum. 950 palladium is more durable than white gold. It is similar to how platinum wears versus white gold. The natural white color of palladium is permanent and unlike white gold, does not require rhodium-plating.
Although silver is classified as a precious metal, in reality, it is a fraction of the value of gold and platinum. Pure silver is far too soft to use for jewelry manufacturing, so it is also alloyed to improve its properties. Silver has a predominant quality known as “Sterling Silver”. For an item to be marked as sterling, it must contain a minimum of 92.5% pure silver alloyed with 7.6% copper. It is also used for flatware services and art objects. Much of the silver that is made into silver jewelry in many other countries, e.g., Mexico, Peru, Germany, etc. is only 80% pure.
While silver is the whitest of metals, has the highest reflectivity, and is the most lustrous. The main problem with sterling silver is that it is prone to tarnish. To prevent this problem, silver can be rhodium-plated in the same way as white gold. However, it is much softer than gold or platinum.
This metallic element in the platinum group is silvery-white, hard, durable, and yet does not normally form an oxide, even when heated. White metal jewelry, such as white gold, and silver can be rhodium-plated to provide protection and prevent tarnish and surface scratches on soft metal. Rhodium also gives the piece a reflective, high-polish, high-shine white surface, looking extraordinarily attractive for a very long time.
Other Non-Precious (Alternative) Metals
This is a very heavy non-precious metal with a black to steel gray to tin-white color or combinations of the colors. Tungsten has the highest melting point and the most tensile strength of all metals. Due to the hardness of this metal, the shine is not apt to fade as with other metals that must be polished. Tungsten also has natural hypoallergenic properties that make it perfect for use in jewelry making. When it is combined with a carbon alloy to create tungsten carbide, it becomes extremely wear-resistant. Unlike all precious metal jewelry that can be sized or repaired, tungsten carbide jewelry cannot be sized or altered.
Titanium is lightweight strong and is a non-precious metal. It is as strong as steel, but 45% lighter in weight. Titanium has a gray metallic color. It is resistant to tarnishing, and 100% hypoallergenic. This metal is used in jewelry in almost its pure form (approximately 99% pure). Unlike precious metals, titanium jewelry cannot be sized or repaired.