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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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TABASHEER OPAL
Tabasheer (also spelled tabashir) or pearl opal is
an organic stone that forms in damaged joints
(nodes) of bamboo plants. This hydrated form of
silica appears as a rounded mass of opal, and looks
like seed pearls.
TABLE
The table is the large, flat area at the top of a
cut gemstone.
TAHITIAN PEARL
Tahitian pearls (also called black pearls) are
dark-colored pearls. They are produced by the large,
black-lipped pearl oyster Pinctada margaritifera
(also called the Tahitian black pearl oyster), a
mollusk found in the tropical Indo-Pacific Ocean.
Black pearls come in many colors, including many
body shades and overtone tints including gray (light
gray to almost black), peacock green (especially
valuable), aubergine (eggplant), and deep brown. The
color of the dark nacre is determined by the
minerals in the oyster's diet (plankton) and in its
environment. Many "black pearls" are dyed or
irridiated to enhance or change their color; it is
difficult to tell a natural pearl from a treated
pearl. Tahitian pearls are graded on six factors:
1.Shape (round is most valued), 2.Size (the larger
the better), 3.Surface Quality= (clean is superior
to blemished), 4.Luster (the more high-gloss luster
the better), 5.Nacre Thickness (thicker is better
and longer lasting), and 6.Color (overtones atop the
body color add value to the pearl. The most
sought-after color is peacock green and darker
colors are more valuable Overtone colors include
blue, pink, gold, silver, aubergine, and peacock
green).
TANVORITE
Tanvorite is a trademarked name for a manmade
gemstone. This synthetic stone is a deep blue-purple
stone that resembles tanzanite.
TANZANITE
Tanzanite (strontium-rich Calcium-aluminum silicate)
is a valuable, transparent, blue-violet type of
zoisite resembling sapphire. Tanzanite has a
hardness of 6 and a specific gravity of 3.35. It is
often heat-treated in order to produce a deeper
blue-violet color. This mineral was discovered in
1967 by Manuel d'Souza (an Indian tailor) southwest
of Mt. Kilimanjaro in Tanzania, Africa.
TAXCO
Taxco is a town in the State of Guerrero in Mexico
that is famous for its silver jewelry production.
The American silversmith William Spratling, set up
shop in Taxco in 1929, and many other silversmiths
followed. Early Taxco jewelry is avidly collected.
Modern pieces are distinguished by a registration
mark of two letters followed by a series of numbers
(this mark was required by the Mexican government
since 1979).
TEMPER
To temper is to strengthen or harden metal (or
glass) by heating it or by heating then cooling it.
Harder tempers are stronger, more spring-like, and
brittler (when they are bent, they may break).
Softer tempers are weaker but bend easily.
TENNIS BRACELET
A tennis bracelet is a simple, flexible, in-line
diamond bracelet. The name tennis bracelet was first
used when the great tennis player Chris Evert
dropped a diamond bracelet during a tennis match in
the summer of 1987 (at the US Open Tennis
Tournament). She had to stop the match until she
found her bracelet. Since then, that style of
bracelet has been called a tennis bracelet.
THERMOLUMINESCENT
Thermoluminescent minerals emit bright light when
heated. For example, chlorophane is a varity of
fluorite that emits bright green light when heated.
THERMOSET PLASTIC
Thermoset plastic (also known as thermoplastic) is a
hard, non-rigid synthetic substance that cannot be
melted by reheating. Thermoset plastic is formed
under high heat or pressure by a process known as
polycondensation. Bakelite is a thermoset plastic.
The bangle above is "butterscotch" bakelite.
TIFFANY SETTING
The Tiffany setting is a ring with a high,
six-pronged solitaire diamond on a simple circular
band. This design was introduced by Tiffany & Co. in
1886.
TIGER'S EYE
Tiger's eye is a yellowish-brown to reddish-brown
gemstone that has a silky luster. This gemstone has
bands of yellow and brown; when viewed from the
opposite direction, the colors are reversed. Tiger's
eye is usually highly polished and set as a cabochon
(or cut as a bead) to display the stone's chatoyancy
(light reflected in thin bands within the stone).
Tiger's eye is a type of chatoyant quartz with
fibrous inclusions (especially crocidolite). This
stone is sometimes heat-treated. Tiger's eye has a
hardness of 7.0. Most tiger's eye is mined in South
Africa, but it is also found in Australia, Brazil,
Burma (Myanmar), India, Namibia, Sri Lanka (Ceylon),
and the USA. Green-grey varieties of this stones are
called cat's-eye quartz. Blue-grey to bluish
varieties are called hawk's-eye. Deep brown
varieties of this stone are called bull's-eye or
ox-eye.
TOGGLE CLASP
A toggle clasp (also called a bar and ring clasp) is
a jewelry fastener in which a bar can be inserted
into a ring to fasten a piece of jewelry. It is used
to attach the two ends of a necklace or bracelet.
TOPAZ
Topaz (aluminum silicate fluoride hydroxide) is a
very hard gemstone that ranges in color from brown,
to yellow to blue to pink. Pink topaz is usually
created by irradiating common yellow topaz. Other
colors are often created by heat-treating and/or
irradiating topaz. Imperial topaz is golden
orange-yellow topaz; it is the most valuable topaz
Topaz has a hardness of 8 and a specific gravity of
3.5-3.6. Topaz may have been named for the legendary
Topasos Island in the Red Sea.
TORQUE
A torque (also spelled torc) is a necklace that
consists of a narrow, twisted band made of metal.
This type of ornament was worn by the ancient Celts,
Britons, and Gauls.
TORSADE
A torsade is a necklace made of many strands that
are twisted together.
TORTOISE SHELL
Tortoise shell is the shell of a tortoise. It was
used in the 1800's for jewelry, hair combs, and
other ornaments but is banned today. Tortoise shell
inlaid with precious metals is called pique.
Tortoise shell will burn easily, and smells like
burning hair. It is easily imitated by plastic, but
its smell when burnt is very different. Tortoise
shell has a hardness of 2.5 and a specific gravity
of 1.29.
TOURMALINE
Tourmaline is a dichroic gemstone that comes in
many, many different colors; it also appears to have
different colors depending on the angle at which it
is seen. Tourmaline has the greatest color range of
any gemstone - thel ighter colors are more valuable
than the darker colors. It ranges in color from pink
to green to red (rubellite) to purple to blue-green
(indicolite) to colorless (achroite) to black.
Watermelon tourmaline is both pink and green.
Tourmaline occurs as an elongate three-sided prism
and is mined in Brazil, The Ural mountains in
Russia, Namibia, Sri Lanka, and California.
Tourmaline was only discovered in the 1700's.
Tourmaline has a hardness of 7-7.5 and a specific
gravity of 3.02-3.25. It is doubly-refractive.
TOURMALINATED QUARTZ
Tourmalinated quartz is a variety of transparent
quartz that has needle-like inclusions of black to
dark green tourmaline crystals. This beautiful stone
is found worldwide. Tourmalinated quartz has a
hardness of 7.0. This stone is not enhanced.
TRANSLUCENT
Translucent materials allow light to pass through
them, but the light is diffused (scattered). Some
translucent stones include moonstones, opals, and
carnelian. Lucite and other plastics can also be
translucent.
TRANSPARENT
Transparent materials allow light to pass through
them without diffusing (scattering) the light. Some
translucent stones include diamond, zircon, emerald,
rock crystal, and ruby. Plastics like lucite can
also be transparent. In the confetti lucite bangle
above, the glitter within the lucite is visible.
TRANSVAAL JADE
Transvaal jade is not jade; it is a green to gray
massive variety of grossular garnet,
calcium-aluminum silicate. It is found about 40
miles west of Pretoria, South Africa. Transvaal jade
can be distinguished from jadeite or nephrite by its
high refractive index. Grossular garnet has a
refractive index of 1.72 to 1.73, a hardness of
6-7.5 and a specific gravity of 3.5 - 3.67.
TRAP ROCK
Trap rock is a type of igneous rock. This solidified
lava often contains pockets of crystals.
TRAPICHE EMERALD
Trapiche emeralds are rare, valuable emeralds that
have a black, six-rayed star within them, caused by
black carbon impurities (the star is not an
asterism). These stones are usually cabochon cut to
display the beautiful spoke-like star. These stones
are only mined in Colombia, South America. Trapiche
emeralds are sometimes called star emeralds (but the
term star emerald can also refer to emeralds with an
asterism). Trapiche is a Spanish word for the spoked
wheel that is used to grind sugar cane.
TREMBLER
A trembler is a piece of jewelry that has a part (or
parts) set on a spring; the spring-set parts move as
the wearer of the jewelry moves.
TRIFARI
Trifari is a pre-eminent jewelry manufacturing
company that produces high-quality and
beautifully-designed pieces. The company began as
Trifari and Trifari in 1910, founded by Gustavo
Trifari and his uncle; a few years later, his uncle
left and the company was simply Trifari. Leo
Krussman joined Trifari in 1917. In 1918, when Carl
Fishel joined the company, they renamed the company
Trifari, Krussman and Fishel (their hallmark was
T.F.K.). Alfred Philippe, who had been a jewelry
designer for Cartier and Van Cleef & Arpels,
designed pieces for Trifari for many years. Some
other Trifari designers included Jean Paris (1958
-1965), Andre Boeut (1967 - 1979), and Diane Love
(1971 - 1974). Trifari was owned by the Hallmark
Company from 1975-1988, and by Crystal Brands from
1988-1994. It was then part of the Chase Capital
division of the Monet Group, which later went
bankrupt and was bought by Liz Claiborne (2000). The
classic pin and earrings set above has paste rubies,
emeralds, sapphires, and diamonds (and was designed
by Alfred Philippe, about 1947-8).
TRILLION CUT
The trillion cut is a triangular cut based upon a
brilliant style cut (and not a stepped facet). The
corners of the triangle are truncated (cut short)
and there are a variety of facets, giving this cut a
sparkling brilliance.
TRIPLET
A triplet is a manufactured stone that is made by
sandwiching three thin layers of stones together.
For example, an opal triplet had a top, protective
layer of clear quartz, a thin middle layer of opal,
and a base layer of dark, color-enhancing matrix
(usually black onyx or ironstone).
TROY WEIGHT
Precious metals (like gold, platinum, and silver)
are measured in troy weight, which has units of
pennyweights, ounces, and pounds. Troy ounces and
pounds are different from everyday US measures.
-
1 pennyweight 24 grains = 1.5552 grams
-
1 Troy ounce = 20 pennyweight 31.1035 grams
-
1 Troy pound = 12 Troy ounces 373.24 grams
TSAVORITE
Tsavorite is a rare, deep green variety of grossular
garnet, a type of garnet, calcium-aluminum silicate.
The emerald green color comes from vanadium and
chromium. Tsavorite is similar to emerald, but is
rarer and more durable; it also has a higher
refractive index, 1.74. Tsavorite stones over two
carats are considered large and are very rare.
Tsavorite has a hardness of 7.5 and a specific
gravity of 3.6. Tsavorite is found in east Africa;
it was named by Harry B. Platt of Tiffany & Co. for
the Tsavo National Park in Kenya, where this
gemstone was originally found in 1967. Tsavorite is
not enhanced.
TUMBLED
Tumbled stones were finished in a tumbler, a
mechanical device that smoothes and rounds the
surfaces of stones. Tumbled stones look very much
like stones that have been in a fast-flowing river
or stream for a long time.
TUMBLER
A tumbler is a rotating cylinder (powered by a
motor) that smooths and rounds the surfaces of
stones, increasing their luster. As the stones
tumble around the cylinder, they bump against each
other and smooth each other's surfaces.
TURQUOISE
Turquoise is a non-translucent, porous semi-precious
stone that is usually cut as a cabochon. Turquoise
was first found in Turkey, hence its name. Turquoise
is found in desert regions worldwide. Persian
turquoise is robin's egg blue and has no matrix
(streaks of the mother stone from which they were
found). North American turquoise is greener and has
a matrix streaks. Over the years, oil from your skin
is absorbed by the stone and it will change color
slightly. Turquoise has a hardness of 6 and a
specific gravity of 2.60-2.85.
TWINNING
Twinning is a common error in crystalization in
which two crystals grow out of one another or next
to one another, and their crystal lattice is
oriented differently from one another (some twins
are like a mirror image of each other). If the
crystals have grown into one another, they are
called penetrant twins (forming a cross-shape like
Staurolite, a star-shape like Muscovite, and other
unusual shapes). If the crystals are mirror images
that grow next to one another, they are called
contact twins (they are often likened to Siamese
twins). Twinning can drastically change the outward
symmetry of the mineral specimen, by either
increasing or decreasing the symmetry (like with
spinel). For example, twinning can make an
orthorhombic crystal appear to be hexagonal (as in
Aragonite).
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