RADIANT CUT
The radiant cut is a method of cutting rectangular stones so that they have the sparkle of brilliant cut round stones. The shape is a rectangle with the corners clipped off - the length:width ratio is usually from 1.5:1 to 1.75:1. This cut has from 58-70 facets; it was invented in the 1970's. The top of the stone is emerald cut (with about 25 facets above the girdle), but the bottom of the stone has brilliant cut facets (with about 36 facets below the girdle).

RAINBOW OPAL
Rainbow opal is a type of precious opal that has curved bands of colors (that resemble rainbows).

RECONSTRUCTED STONE
A reconstructed stone is one that is made from pieces of smaller stones or crystals). Reconstructed stones often have telltale air bubbles. For example, "Geneva rubies" (reconstructed rubies) are made from tiny ruby crystals that have been fused together. This type of stone is no longer manufactured (except reconstructed amber, which is stilll made) because synthetic stones are vastly superior to reconstructed stones.

RED BERYL
Red beryl is a is a rare, deep red variety of beryl. Gemstone-quality forms of this mineral are found in only one place in the world, in the Wah Wah Mountains, near Beaver, Utah, USA. Small crystals of this gem were first found in 1905 in the Thomas Range in Juab County, Utah. The mine bearing gemstone-quality red-beryl was found in the 1950's. The biggest red beryl crystal ever found was 14mm by 34mm, weighing about 54 carats. The average faceted red beryl gemstone weighs about 0.15 carats. Red beryl has a hardness of 7 - 8, a specific gravity of 2.66-2.70, and a refractive index of 1.564-1.574.

REFRACTION
When light enters a medium with a different optical density (like a gemstone), the light is bent at an angle (and also changes its speed).

REFRACTIVE INDEX
The refractive index is a measure of how light is refracted in a substance (like a gemstone). In doubly-refractive stones, the light is split into two light rays when it enters the stone, and the rays travel in different paths - so these stones have more than one refractive index.

REFRACTOMETER
A refractometer is a device that measures the refractive index of a gemstone.

RHODOCHROSITE
Rhodochrosite is a mineral whose color ranges from rose to pink to almost yellow or brown. Although it is very pretty, this stone is soft and brittle; it is used in jewelry and for carvings and figurines. Rhodochrosite is Manganese Carbonate; its chemical formula is MnCO3. Rhodochrosite has a hardness of 3.5 - 4.5 (glass has a hardness of 4) and a specific gravity of 3.5. Rhodochrosite is found in Argentina, Peru, Germany, Mexico, South Africa, Russia, Italy, USA (Colorado and Montana), and Romania. Rhodochrosite is not enhanced.

RHODOLITE
Rhodolite (meaning rose stone in Greek) is a purple-red to pink-red variety of garnet and is a combination of almandine and pyrope (it is sometimes called pyrope-almandine garnet). This silicate stone has a hardness of 7-7.5 and a specific gravity of 3.5 - 4.3. The formula for garnet is: A3B2(SiO4)3. Rhodolite is found in the US, Zimbabwe, Kenya, and Sri Lanka (Ceylon). Rhodolite is not enhanced.

RING
A ring is a piece of jewelry worn around the finger; rings have been worn on every finger, including the thumb. Rings have been worn through the ages, and often have significant meaning. Some rings include wedding and engagement rings (denoting commitment), signet rings (impressed with the owner's seal), bands (made from a ribbon of metal), rings denoting group membership (like Masonic rings or college rings), devotional rings (with religous meaning), and pugilist rings (pointed rings worn by boxers to harm their opponent).

ROCAILLE
Rocaille is jewelry whose design is based on sea life, sea shells, or rocks.

ROLLED GOLD
Rolled gold is a very thin sheet of gold that is laminated to a lesser metal (usually brass). The two layers of metal are heated under pressure to fuse them together. The sheet is them rolled into a very thin sheet and then used to make jewelry or other objects. Jewelry made from rolled gold wear well over time. Rolled gold pieces are marked rolled gold plate, R.G.P., or plaqu? d'or lamin?.

RONDELLE
A rondelle is a small disc used as a spacer in beadwork. Some rondelles are clear crystal discs, often used between colored crystal beads. Other rondelles are encircled with chanel-set diamonds or rhinestones.

ROPE
A rope is a string of pearls that is over 40 inches long.

ROSE CUT
The rose cut (also called the rosette cut) for diamonds was invented in the 17th century and its used continued until the 18th century. The rose cut has a flat base and triangular facets (usually 24). This cut has little wastage of stone, but is not nearly as reflective as the brilliant cut, which was invented later.

ROSE QUARTZ
Rose quartz is a form of quartz that ranges in color from pink to deep red.

ROUGH
Rough stones or crystals are in their natural state, they are neither cut nor polished.

RUBELLITE
Rubellite (sometimes spelled rubelite) is a red variety of tourmaline. Rubellite is red in both incandescent and daylight, and is more valuable than other varieties of red tourmaline. Rubellite has a hardness of 7-7.5 and a specific gravity of 3.02-3.25. Rubellite is sometimes treated with fillers to increase the clarity of the stone.

RUBY
Rubies are precious stones and a member of the corundum family. Rubies range in color from the classic deep red to pink to purple to brown. Rubies are extremely hard; only diamonds are harder. During the renaissance, people thought that rubies could counteract poison. Laboratory-produced rubies were created in the 1890's; they are difficult to distinguish from natural rubies. The biggest ruby in the word is the Raviratna, which weighs 3,600 carats. Rubies have a hardness of 9 and a specific gravity of 3.9 - 4.1. Rubies are found in Afghanistan, Australia, Brazil, Cambodia, India, Myanmar (Burma), Malagasy Republic, Malawi, Pakistan, Sri Lanka (Ceylon), Tanzania, Thailand, United States (Montana and North Carolina), and Zimbabwe (Rhodesia)

RUSSIAN GOLD FINISH
A Russian gold finish is a matte, antique-look finish. Miriam Haskell jewelry often has a Russian gold (plated) finish.

RUTILATED QUARTZ
Rutilated quartz is a type of rock crystal which contains long, fine needles of rutile crystals (titanium dioxide). This beautiful stone is usually cut as a cabochon. It is also known as Venus' Hair Stone.