Whether it’s understanding gemological or jewelry terms in an article you’re reading or simply gaining a greater understanding of the world of jewelry and gemstones, our Jewelry & Gem Dictionary is a handy reference guide. And, unlike most dictionaries, ours makes for interesting reading all on its own!

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 calsilica is a newly-found, multi-colored, layered stone composed of calcium and silica. This stone has been recently used for Zuni fetish carvings and in some jewelry (beads and cabochon cut stones). Rainbow calsilica was only recently found in Mexico or Northern South America (it’s origin remains mysterious). Some people theorize that this stone formed as a result of the runoff of mining or oil-drilling chemicals, and has only formed in the last 30 to 50 years (but this is uncertain).

Rainbow obsidian is another name for obsidian that is iridescent.

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

Rainbow topaz (also called mystic topaz or mystic fire) is topaz that has been color enhanced by coating it with a fine layer of metal atoms (in a process called vacuum deposition). This stone has red, green, violet, and blue streaks. Mystic fire has a hardness of 8.

The Rajaratna is the biggest-known “star ruby” (a ruby that exhibits an asterism, a six-pointed star of light, cut as a cabochon). It weighs 2,475 carats.

The rati is an Indian unit of weight that is used for gemstones. A rati is equal to 0.91 carats. The rati has varied in the past (and in different regions).

The Raviratna is the biggest-known ruby. It weighs 3,600 carats.

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 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.

Red diamonds are rare, fancy diamonds and are quite valuable. Diamonds are precious, lustrous gemstones made of highly-compressed carbon; they are one of the hardest materials known. Diamonds have a hardness of 10, a specific gravity of 3.5, and a refractive index of 2.417 – 2.419.

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).

The refractive index is a measure of how light is refracted in a substance (like a gemstone)—the ratio of the velocity of light in air to its velocity in the new substance. When a ray of light meets the surface of a polished gem, some of the light is reflected, but most is absorbed. Because of the difference of density between air and gemstone, the light entering the gem slows down and is bent from its original path (refracted). The refraction varies from gem to gem depending on density and can be measured and used to help identify the gem type. This measurement is called the refractive index or RI. Almost every gem material has its own unique specific refractive index (RI). Determination of the RI is probably the most conclusive measurement available to gemologists. 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.

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

Repousse is a method of decorating sheet metal in which designs are hammered into the back of the metal. Special punches are used to form the designs, which form in relief (raised designs) on the surface of the metal.

Retro jewelry is chunky, geometric jewelry from the 1940’s. Pink gold was often used in retro pieces.

Rhinestones are highly reflective glass made to imitate gemstones. The original rhinestones were quartz stones (rock crystal) obtained from the Rhine river. These stones were cut to resemble gemstones. The best rhinestones today are made of highly reflective leaded glass which is faceted and polished.

Rhodium is a white precious metal. Rhodium is extremely expensive and is often used to plate precious and base metals, giving jewelry a hard, platinum-like sheen.

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 (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.

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 religious meaning), and pugilist rings (pointed rings worn by boxers to harm their opponent).

Rings are sized using a graduated cone (a mandrel) with markings denoting the ring sizes. The ring is put on the cone and its size is read where it fits snugly on the cone. To size a finger, a finger-ring gauge is used. The rings are marked with their size and the person determines which one fits well. Another, less accurate method, is a cardboard card with cut-out holes marked with the ring sizes. Sizes in the US and Europe are numerical; sizes in the UK are alphabetical. To determine the ring size of a finger using the circumference of the finger, or to determine the size of a ring given its diameter, the formulas are:


Circumference in mm = 36.107 + (2.5890*Ring Size)
Diameter in mm = 11.4931 + (0.8241*Ring Size)

Ring Size =Circumference in mm
Ring Size = 3.1416 * Diameter in mm

Circumference in mm = 36.667 + 1.2368*Ring Size(where 1=A, 2=B, etc.)
Diameter in mm = 11.6713 + [0.3937 * Ring Size(where 1=A, 2=B, etc.)]
Riverstones are smooth, rounded pebbles found in rivers and on beaches. The action of the water and other rocks on riverstones polishes them naturally. Riverstones can be used as beads/stones in jewelry.

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

Rock crystal is a transparent, crystalline mineral. Rock crystal is the purest form of quartz and a semi-precious stone.

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?.

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.

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

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 gold (also known as pink gold) is gold with a pink tinge. It has been alloyed with a mix of 90% copper and 10% silver.

Rose de France is a recent name for a very pale variety of amethyst. It is also known as lavender amethyst. Rose de France has a hardness of 7.0. This pale lilac transparent gem is found worldwide and is a type of quartz. Rose de France is sometimes heat-treated in order to lighten its color and/or to remove smokiness.

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

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

Roulz is a metal alloy that consists of about copper, nickel, and silver. Ruolz is named for the French chemist and musician Vicomte Henri de Roulz, who invented the alloy in the 1800s.

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.

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)

A ruby spinel (or spinel ruby) is deep red, transparent spinel (not a ruby).

Rumanite is a type of opal that is from Romania.

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

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.

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