In order to determine the karat weight of a specific item, simply look for the quality mark. Jewelry items will bear the stamp of their karatage based upon the United States or European system of marking. The United States system designates pieces by their karats—24K, 18K, 14K, 10K, etc. The European system designates pieces by their percentage of gold content. For instance, 10K gold is marked “417,” denoting 41.7% gold; 14K is marked “585,” denoting 58.5% gold; and 18K is marked “750,” denoting 75% gold; etc.

Yellow Gold
By far the most common color of gold used in jewelry, yellow gold is gold in its natural shade. Yellow gold is usually alloyed with copper and silver to increase the strength of the metal. How yellow the metal is depends upon the content of gold. A 14-karat piece of jewelry will have a brighter yellow hue than a 10-karat piece. Likewise, an 18-karat piece of jewelry will have a deeper yellow than 14-karat gold, and so on.

Amethyst
Amethyst, the most precious member of the quartz family, exhibits purple shades ranging from pale lilac to deep purple, sometimes exhibiting reddish or rose overtones. Very deep-colored amethysts are the finest and most highly valued . Some stones are so over-saturated with color they have areas that are blacked out, which can negatively impact their value. Paler shades, sometimes called "Rose of France," were common in Victorian jewelry. Banding—darker and lighter zones of color—is also a common occurrence. Occasionally, amethyst is even found combined with its sister quartz, citrine, into a single stone called ametrine.

The birthstone for February, amethyst is an extremely popular gem for jewelry because of its regal color, variety of sizes and shapes, affordability and wide range of hues. It also is the recommended gem for couples celebrating their 6 th and 17 th wedding anniversaries. With a hardness of 7.0 on the Mohs Scale, amethyst can occur as long prismatic crystals that have six-sided pyramids at either end, or can form as drusies that are crystalline crusts that only show the pointed terminations.

The ancient Greeks believed that amethyst made one immune to the effects of alcohol. In fact, the name even comes from the Greek word amethystos, which means “not drunken.” Legend has it that the amethyst originated from Bacchus, the god of wine. Bacchus became angry at the mortals and vowed that the next mortal to cross his path would be eaten by tigers. Amethyst, a beautiful young maiden, was on her way to worship the goddess, Diana. Diana turned her into colorless quartz to keep her from being eaten. Bacchus observed the miracle and repented his hasty decision. He poured wine over the young maiden, leaving her feet and legs colorless. This is the reason that amethyst crystals are usually uneven in color and have a colorless base at the bottom. Because amethyst was believed to prevent drunkenness, wine goblets were often carved from it in ancient Greece. Today, the gem still symbolizes sobriety.

Amethyst has been a part of history throughout the ages. Evidence suggests that prehistoric humans used amethysts for decoration as early as 25,000 B.C. Legends suggest that the Egyptian queen Cleopatra wore an amethyst signet ring, as did Saint Valentine, who bared an amethyst engraved with the figure of Cupid. During medieval times, people used the stone as medication to stay awake and alert. Leonardo Da Vinci claimed that amethyst could dissipate evil thoughts and quicken the intelligence. In some legends, the stone represents piety, celibacy and dignity. In the Middle Ages, for instance, the gem was an important ornamentation for the Catholic Church and other religions. It was considered the stone of bishops, and they still often wear amethyst rings. In Tibet, amethyst is considered sacred to Buddha and rosaries are often made from it. Amethyst has also long been a favorite of kings and queens for its royal purple hues that symbolize wisdom, strength and confidence. Amethysts are even featured in the British Crown Jewels and were worn by Catherine the Great.

Amethyst’s availability and magical qualities make it the stone of preference in ancient lore and mysticism. As a meditation stone, it is said to quiet the mind, promote contemplation, sharpen psychic powers and uplift the spirit. It is a stone of deep wisdom. Folklore says it can quicken the wit, calm fears and ward off anger. It has a royal purple essence that is said to lend courage to travelers, scare off thieves and protect travelers from harm. Placed under the pillow or worn to bed, there are claims it promotes peaceful sleep and pleasant dreams. Amethyst can also be worn to supposedly make the wearer gentle, amiable and happy.

The stone is mined in Brazil, Uruguay, Bolivia and Argentina, as well as in Zambia, Namibia and other African nations. Very dark amethyst in small sizes also is mined in Australia. But the ideal for fine quality amethyst was set by a Siberian variety, often called Russian or Uralian amethyst, which is now considered a defunct source. Generally, South American amethyst tends to come in larger sizes than African amethyst, but the African variety has a reputation for having deeper color intensity and is therefore considered more valuable. The African version also is harder to come by than amethyst mined from South America. Most of today's amethyst comes out of Brazil.

Lune de France is a very special variety of amethyst that rarely comes to market. From the northwest state of Amazon in Brazil, this gemstone comes from the Maraba mine. This lovely lilac gemstone features a unique velvet-like quality that at first observation can be confused for an opal or moonstone. The gemstone's internal structure contains natural, cloud-like veils of microscopic inclusions that are extremely minute, even under high power magnification. These inclusions cause the incoming light to scatter and reflect, thus creating an opalescent effect. While a similar inclusion structure can be expected in rose quartz, it almost never occurs in an amethyst. Lune de France features a natural lilac color and retains excellent transparency allowing it to be faceted for maximum light play.

Earring Back Types

Butterfly Back: A double looped piece resembling a butterfly that fits over a post. Variations on this design are called push back clasps. The basic post and butterfly back are usually used for stud earrings and lighter weight drop earrings.

Hinged Snap Backs: This clasp features a hinged post that snaps into a groove on the back of the earring. It is commonly found on hoops. Sometimes the hinged post is curved to provide more room to fit around the ear, sometimes called a saddleback.

Hook Backs: This earring backing is simply a long, bent post that fits through the piercing. Hooks have several variations, most notably the shepherd's hook and the French hook. While thin wire hooks reduce the weight of long earrings, making them more comfortable, they aren't as secure as other clasp styles.

Lever Back: A hinged lever snaps shut against the curved post to form a closed loop around the ear lobe. This clasp is very secure and good for large or medium sized styles that drop just below the ear.

Omega: Also called French clips, this clasp has a straight post and a looped lever. The hinged lever closes around the post and is held against the ear with pressure. The omega clasp is the most secure clasp, especially for the larger, heavier earrings.

Screw back: This backing is a slight variation of the standard post and butterfly nut back. Instead of pushing on the back, the nut twists onto the threaded post. A screw back post design is often preferred for expensive diamond stud earrings that require increased security.