Opal and .60 ct. t.w. White Zircon Starburst Locket Necklace in 18kt Gold Over Sterling. 20"

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."

HAMMERED: A dimpled finish that looks as if it were applied through various strikes of a hammer. The result is a random, banged-out look with an artisanal appeal. A hammered piece can appear either matte or polished.

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.

OPAL: With an iridescent luster that can reveal a beautiful kaleidoscope of color, the opal has inspired many myths and legends. A white opal with swirls of soft pastel shades is popular for jewelry, but opals also come in black and blue. Opal is the gemstone for October birthdays.

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

ZIRCON: Gem-quality zircon is a transparent crystal from the mineral zirconium silicate. It comes in a variety of colors, most popularly blue and colorless. Contrary to common belief, zircon is not Cubic Zirconia; it is a naturally occurring gemstone with different properties.