Articles - Materials

Gold jewelry is described in terms of karatage (caratage), as an indication of its gold content. Pure gold is 24 karats, although it is much too soft to be used in jewelry making, which is why fine gold jewelry is so rare. As a rule, gold used in jewelry is an alloy of gold and other metals such as silver and copper.

Various karatages and their equivalent gold content (in percent or in fineness terms) are recognized by international standards. Some popular caratage groups are:

21-22 karats – also marked as 916 or 875 fineness
18 karats – also marked as 750
14 karats – also marked as 585
9 karats – also marked as 375.

Some jewelry, in particular antique pieces, is not hallmarked for its gold content, and may be assayed by a simple method that uses a chemical substance.

Platinum has been used in jewelry making since the beginning of the 20th Century. A chemical element with the symbol PT, it is white in appearance. It is more precious than 22 karat gold and is widely used in prestigious jewelry.

In the world of jewelry, silver is considered to be a "second rate" precious metal, having a much lower price tag than gold. Pure silver is denoted by the number 999, however it is never used in its pure form in jewelry and silverware because of its softness.

The highest silver content in use is 925 and is called sterling silver. Sterling silver is standard mainly in England, the US and France. Lower silver alloys are marked with 900 and 800 and are standard mainly in central and eastern Europe (in Russia, silver had been marked with 840 before the Soviet Revolution, and with 875 thereafter).

Many countries also have their own hallmarks for silver, such as the crown and moon seen on German silver, the eagle of the French, etc.

Rose Cut Diamonds are distinguished from modern diamonds in their cut, which primarily affects the brilliance of the stone. The Rose Cut Diamond cut is made to resemble an opening rose bud, hence its name.

A characteristic of the Rose cut is that it is flat below, and forming a hemisphere or low pyramid above, covered with small facets. The facets are in two rows: those in the upper row are called star-facets; those in the lower diagonal facets. In the centre there are usually six triangular facets. Three to four sided, these facets vary in number in each stone – between three or four up to 24 facets per stone.

The cut makes the Rose Cut Diamonds lighter than the later diamonds, with softer, grayer appearance and less brilliance and clarity. Diamonds arrived in Europe in the Middle Ages and first appeared in jewelry in the 15th Century.

The more modern diamond cut is called Brilliant, as it is designed to bring out the brilliancy and lustre of the stone. In early brilliants, there is a smaller "table" and the crown and the facets are higher. This cut had been designed to eliminate waste in the process of cutting and give the gem maximum weight. Later on, as the demand for brilliancy and sparkle was growing, proportions changed, with the crown getting bigger and the facets shorter.

Another form of cut characteristic of old jewelry diamonds is called Altschliff (literally, in German, old cut) in which the bottom facets do not meet to create a point; instead, there is a space remaining which looks like a "cavity".

The weight of diamonds is measured in carats, each carat being one fifth of a gram.

Other gemstones, besides diamonds, are sapphire, ruby and emerald. They are defined as precious because of their relative rarity and hardness, which makes them more difficult to process. However, this hardness also makes them able to withstand heat to high degrees, thus  goldamiths can create jewelry items , using high heat around them.

Sapphire is a variety of the mineral corundum. It appears in a variety of colors except red. Ruby is the red variety of the same mineral, its red color caused mainly by the presence of the element chromium. Emerald is a green gemstone of the mineral beryl. The quality and price of Sapphire, Ruby and Emerald are determined by the color and clarity of the stone, as well as its hardness, cut style and sometimes place of origin.

The semi-precious gemstones are more abundant in nature and are not as hard to process. Consequently they are significantly less expensive than the precious gemstones. Some of the popular semi-precious stones are aquamarine, amethyst, citrine, opal, turquoise, tourmaline, quartz, jade and others.

Natural pearls grow within a living shelled mollusk. There are two groups of "genuine" pearls: natural, and cultured. A "natural pearl" is one that forms in the wild, without any human intervention, and is very rare. A "cultured pearl" is one that has formed in the shell of a mollusk with the helping hand of man, by implanting a core or nucleus into pearl oysters. Since the mid 20th Century, due to overfishing of seawater pearl oysters and increasing ocean pollution, natural, wild pearls have become extremely rare. Practically all pearls sold today across the world are cultured.

There are two kinds of cultured pearls: Saltwater pearls, growing in seas and bays, and freshwater pearls, cultured in lakes and rivers. Saltwater pearls are of higher quality than freshwater ones (they have a thicker nacre and a softer luster) and are therefore more expensive.

The two most common types of saltwater pearls are the Japanese akoya pearls, and South Sea pearls – currently cultured in areas throughout the Indian and Pacific Oceans, primarily in Australia, the Philippines, Indonesia and Myanmar. The South Sea pearls are characteristically large – between 9-19 mm.

The quality of freshwater pearls has greatly improved in recent years; they are widely available, and they look great, with a good nacre thickness, so that only experts would be able to distinguish them from saltwater pearls.