.90 ct. t.w. Swiss Blue Topaz Sailboat Pendant Necklace with Diamond and Sapphire Accents in 18kt Gold Over Sterling. 18"

18KT: Karat (abbreviated kt or K) is a unit that indicates the purity of gold in the metal. 18kt is 75% gold. In Europe, 18K yellow gold is most favored and used in jewelry.

YELLOW GOLD: Gold is a precious metal with a natural yellow color. It is quite soft and often alloyed with other metals to increase its strength. The purity of the metal is indicated by a unit called a "karat," with 24kt having the highest percentage of natural gold.

STERLING SILVER: Also known as "Standard Silver," sterling silver is silver alloyed with other metals to increase the hardness and durability. Generally, sterling is 92.5% silver and 7.5% other metals. Some sterling silver jewelry is plated with 14kt-18kt gold and referred to as "vermeil," or "gold over sterling."

CABLE: One of the most popular and classic of chain styles, created from interlocking oval links unvarying in size.

LOBSTER CLASP: named after the pinching style of the hook, this clasp is often shaped like a lobster's claw. Use your finger to work the lever to open the clasp.

MOTHER-OF-PEARL: Glowing with an iridescent beauty, mother-of-pearl has been showcased in jewelry designs for thousands of years. As mother-of-pearl is a natural substance, it may vary in appearance, and its distinctive shimmer lends a quiet elegance to fine jewelry.

SLICE: A thin, usually flat piece cut from a gemstone. Often has a free-form shape and reveals the natural beauty of a gemstone's interior.

SAPPHIRE: A favorite gemstone of ancient priests and royalty, the sapphire radiates sophistication and grace. This prized gem comes in every hue of blue, plus the more unexpected shades of pink, yellow, green and orange, and is September's birthstone.

TOPAZ: Available in a stunning selection of shades, the topaz's sky blue hue is one of the most popular colors for jewelry designs. Once thought to offer protection, today topaz is favored for its durability and affordability. Yellow topaz is the birthstone for November while blue topaz is for December.

Diamond: The hardest and most brilliant of all gemstones, a diamond can make the heart race with its pure and fiery spark. An ancient symbol of love, a diamond is the preferred gemstone for tokens of affection, such as rings, earrings, necklaces and bracelets. Diamond is the birthstone for April.

SINGLE-CUT: A gemstone cutting technique that dates back to the 1300s. Still used today, the single-cut usually features 18 facets that go in one direction without crossing each other.