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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!
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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 CALSILICA
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
Rainbow obsidian is another name for obsidian that
is iridescent.
RAINBOW OPAL
Rainbow opal is a type of precious opal that has
curved bands of colors (that resemble rainbows).
RAINBOW TOPAZ
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.
RAJARATNA
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.
RATI
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).
RAVIRATNA
The Raviratna is the biggest-known ruby. It weighs
3,600 carats.
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 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 DIAMOND
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.
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)—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.
REFRACTOMETER
A refractometer is a device that measures the
refractive index of a gemstone.
REPOUSSE
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
Retro jewelry is chunky, geometric jewelry from the
1940's. Pink gold was often used in retro pieces.
RHINESTONES
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
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
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 religious meaning),
and pugilist rings (pointed rings worn by boxers to
harm their opponent).
RING SIZE
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:
-
USA
Circumference in mm = 36.107 + (2.5890*Ring
Size)
Diameter in mm = 11.4931 + (0.8241*Ring Size)
-
Europe
Ring Size =Circumference in mm
Ring Size = 3.1416 * Diameter in mm
-
UK
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.)]
RIVERSTONE
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
Rocaille is jewelry whose design is based on sea
life, sea shells, or rocks.
ROCK CRYSTAL
Rock crystal is a transparent, crystalline mineral.
Rock crystal is the purest form of quartz and a
semi-precious stone.
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 GOLD
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
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
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.
ROULZ
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
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)
RUBY SPINEL
A ruby spinel (or spinel ruby) is deep red,
transparent spinel (not a ruby).
RUMANITE
Rumanite is a type of opal that is from Romania.
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.
SPJ's Favorite Sources
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