C. 1950 Vintage Black Onyx and Carnelian Ring with Diamond Accents in 18kt White Gold. Size 5.75

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.

WHITE GOLD: Gold is a precious metal which is naturally quite soft. To give it a white color and increase its strength, gold is alloyed with white metals, such as silver and/or palladium, and often plated with rhodium. The purity of the metal is indicated by a unit called a "karat," with 24kt having the highest percentage of natural gold.

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.

CLARITY SI1: Slightly Included. Inclusions are noticeable under 10x magnification.

CARNELIAN: A brownish-red mineral, carnelian has been used for centuries to make engraved gems and signet rings, intaglios and especially seal rings, because hot wax does not adhere to it. Its name comes from the Latin word for cherry, since the lush red color of the carnelian so resembles the vivid red fruit.

CABOCHON: A style of cutting gemstones to achieve a smooth, domed surface with an absence of facets.

ONYX: A favorite of the ancient Greeks and Romans, this gemstone adds a sophisticated shine to rings, necklaces, bracelets and earrings. A dyed form of chalcedony, onyx is most popularly found in black although it can be green, white or red, as well.