LAB RUBY (SAPPHIRE)
A lab ruby (or sapphire) is a synthetic (laboratory-made) stone. It has the same composition, hardness, and specific gravity as natural rubies (or sapphires) but is much less expensive than a natural stone (since they are relatively inexpensive to create in the laboratory as comared to mining gemstones). These lab-produced stones can be legally referred to as "real" stones [as opposed to "natural" (mined) stones].

LAPIDARY
A lapidary is someone who cuts and polishes gemstones.

LAPIS LAZULI
Lapis lazuli is a rich blue opaque, semi-precious stone that has been used in jewelry since ancien times. Ground-up lapis lazuli was once used as a pigment for oil paintings. Lapis lazuli is often dyed to deepen and improve its color. Lapis has a hardness of 5.5; it chips and scratches easily. It has a specific gravity of 2.4 to 2.9. Water can dull its sheen. Lapis lazuli contains the minerals calcite (which decreases its value), pyrite (which can increase its value), and sodalite. Swiss lapis is not Lapis lazuli at all; it is dyed jasper. Denim lapis is relatively pale, low-grade, inexpensive lapis from Chile; it is the color of denim cloth because of calcite inclusions (which whiten the color and lower the value).

LAVALIER
A lavalier is a pendant with a dangling stone that hangs from a necklace. Lavaliers were named for the infamous Duchess Louise de La Valliere (1644-1710), a French woman who was a mistress of the French king Louis XIV (and was involved in many intrigues at court).

LEAF
Metallic leaf is paper-thin sheets of metals. For example, gold, silver, platinum, and copper are rolled or pounded into metallic leaf which can be applied to surfaces.

LENTIL CUT
A lentil cut stone is a cabochon cut in which the upper and lower portions of the stone are identical.

LOBSTER CLAW CLASP
A lobster claw clasp is a jewelry fastener that resembles the claw of a lobster. A tiny spring keeps the arm of this clasp closed. It is used to attach two other rings or links of a necklace or bracelet.

LOCKET
A locket is a pendant that can open up. Lockets can hold photos, hair, a charm, or other small, precious object.

LOST WAX CASTING
Lost wax casting is a process of casting metal in which the original model is sculpted in wax. The wax is then enclosed in clay and the wax is melted out, making a hollow mold. The mold is then filled with molten metal. The clay is broken off and the cast metal remains. This method of casting has been used for at least 4,000 years.

LOZENGE
A lozenge has a diamond shape. A lozenge cut stone is a step-cut gem with a diamond shape.

LUSTER
A stone's luster is its sparkle or sheen - the way it relects light. The luster depends on the nature of the stone's surface reflectivity. Some types of luster include: adamantine (also called brilliant or diamondlike, like a faceted diamond), earthy (with little reflectivity- also called dull, like shale or clay), greasy (like nepheline or apatite), metallic (also known as splendent, like pyrite or marcasite), resinous (like amber), pearly (with an iridescent reflectivity, like pearls or mica), pitchy (tarry minerals that are radioactive, like uraninite), silky (with a fibrous structure, like some tiger's eye or satin spar), vitreous (also known as glassy, like olivine, transparent quartz, or obsidian), and waxy (like halite or turquoise). A pearl's luster is derived from its nacre.