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NATURAL GEMSTONES: "Natural gemstones" refers to those gems
formed in the earth, whether or not they have been treated after mining.
NICKEL SILVER: An alloy of copper, nickel, and zinc, also known
as German Silver, first gaining popularity in the 1830s. Please refer to
the
Precious Metals Buyer's Guide
for more information.
NUTMEG GRATER: A small box, made from the 17th century to the
middle of the 19th century, with a removable grate under the lid for the
grating of precious spices such as nutmeg.
NUUMMIT:
Click on the link and learn everything there is to know about this gem
type from Thaigem.com's extensive resources of information.
OF: An abbreviation
representing an open-face watch, which is a watch with a cover on the
reverse and a crystal only over the face on the obverse.
OLD EUROPEAN CUT: Style of cutting popular in the 19th century,
direct predecessor of the modern round brilliant cut. Old European cuts
have a smaller table than the round brilliant cut, and overall depth is
somewhat greater.
OLD MINE CUT: In general, a diamond cut into an early style of
round cut, prior to the modern round brilliant cut. Apparently it was
mistakenly believed that diamonds were once cut at the mines before
wholesaling.
OMEGA BACK: A hinged fastening clasp that closely resembles the
Greek letter, Omega. Used to secure earring posts to the ear.
ONLAY: A decorative feature of an item of jewelry, such as a
gemstone. Please refer to the
Jewelry Setting Buyer's Guide for more
information.
OPAL: Click on the link and learn everything there is to know about this gem
type from Thaigem.com's extensive resources of information. Click here
for the on-line catalogue of this gem type.
OPALESCENCE: This term refers to a milky blue form of
iridescence.
OPTICAL EFFECTS: Some gems exhibit unusual optical effects known as
phenomena. These rare and beautiful effects very often add value to
gems. The Cat's Eye Effect (CHATOYANCY), the Star Effect (ASTERISM), the
Color Change Effect (COLOR CHANGE), (AVENTURESCENCE) and (IRIDESCENCE)
are very popular phenomena and are highly valued.
ORE: A rock that contains metals capable of being extracted for
commercial usage.
ORGANIC GEMS: A gem type made by or derived from living
organisms, such as pearls from oysters and amber from tree resin.
PALLADIUM: A rare and expensive
precious metal used as an alloy with gold to create white gold. Palladium
increases the value of white gold to above that of yellow gold. Please
refer to the
Precious Metals Buyer's Guide
for more information.
PARURE: A matching suite or set of jewelry usually including a
necklace, pendant, brooch, earrings, and a bracelet.
PARTI-COLORED GEMS: These are crystals that are made up of different
colored parts. They may be made up of two colors, in which case they are
called bicolor, three colored, in which case they are called tricolor,
and sometimes more. This color phenomenon is superbly exhibited in
Tourmaline,
which in some cases can exhibit as many as 15 different colors or shades
within one crystal.
PASTE: Colored or clean glass, often lead or flint glass, which
is cut in the same fashion as gemstones. Antique paste jewelry was valued
on its own merits and not as an imitation.
PAVE SETTING: "Pave" settings produce a carpet of brilliance
across the entire surface of a piece of jewelry. The surface is
encrusted, or quite literally "paved" in diamonds and gems, and the
body of the jewelry is brought vibrantly to life. Please refer to the
Jewelry Setting Buyer's Guide for more information.
PAVILLION: The lower part of a cut gemstone, below the girdle.
PEARL: Click on the
link and learn everything there is to know about this gem type from Thaigem.com's
extensive resources of information.
Click here for the on-line
catalogue of this gem type.
PECTOLITE:
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type from Thaigem.com's extensive resources of information.
Click here for the on-line catalogue of this gem type.
PEGMATITE: An igneous rock formed as residual liquids from magma
cool down these often form large crystals.
PERIDOT: Click on the
link and learn everything there is to know about this gem type from Thaigem.com's
extensive resources of information.
Click here for the on-line
catalogue of this gem type.
PETALITE: Click on
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Thaigem.com's extensive resources of information.
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PHENAKITE: Click on
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Thaigem.com's extensive resources of information.
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PINCHBECK: Christopher Pinchbeck, 1670-1732, was a London jeweler,
watchmaker, and alchemist who invented a substitute for gold made from
an alloy of copper and zinc.
PINWIRE: A round wire used for the manufacturing of brooch pins
and earwires. The wire is supplied hard so that it maintains its shape
and rigidity during use.
PIQUE: Tortoise shell or ivory that has been inlaid with gold,
silver, or mother-of-pearl.
PLACER DEPOSIT: A concentrated secondary deposit of minerals located
usually in rivers and/or seas.
PLATING: The covering of base metal articles with a layer of gold
or silver, which may be of various thickness and grades. Presence of
plating may be discovered by filing and using nitric acid or by
subjecting the item to specific gravity testing. Please refer to the
Precious Metals Buyer's Guide for more information.
PLATY: A habit characterized by thin, flat plate-like crystals.
PLATINUM: Sixty times rarer than gold, platinum is only found in a
few locations worldwide. Platinum is relatively new to the jewelry
market and is already a bedrock of the contemporary jewelry landscape.
Purer, stronger and denser than gold, platinum is considered by many
to be the ultimate and most luxurious of all the precious metals.
Please refer to the
Precious Metals Buyer's Guide
for more information.
PLATINUM MARKS & STAMPS: Platinum should always carry a
stamped mark upon it, which states its purity. U.S. law dictates that
if a purity mark appears, then you should also be able to see the
manufacturer's trademark. U.S. law also states that platinum with a
purity of less than 85% cannot legally be called platinum. Modern
platinum jewelry is usually stamped with a simple purity mark such as
950 or PT950. Please refer to the
Precious Metals Buyer's Guide
for more information.
PLATINUM PURITY: Platinum's purity is expressed differently than
gold. Instead of expressing purity in ratios of 24 parts, platinum
standards are expressed as units of a 1,000 parts. The most regular
platinum purities seen are: Please refer to the
Precious Metals Buyer's Guide
for more information.
950 Plat - 95 percent pure platinum.
900 Plat - 90 percent pure platinum.
850 Plat - 85 percent pure platinum.
PLEOCHORIC GEMS: These are gems that display one color from one
direction, but exhibit one or more other colors or shades when seen from
another direction.
PLIQUE-A-JOUR ENAMEL: Transparent enamel placed between thin strips
of metal that are soldered together to form the design, the end result
of which is similar to stained glass. Plique-a-jour is distinguished from
cloisonné in that there is no base on which the strips of metal and enamel
rest.
POLISHED STONE: Decorative gemstones given a flat, polished surface
used in ornaments and jewelry.
POLISHING: The shine given to the surface of a stone – either by
rubbing it with powder or grit, or against another gemstone – is its polish.
Opaque and darker colored gemstones, opal and turquoise, are often polished
as opposed to faceted.
POLYCHROME ENAMEL: Enamel in various colors.
POLYCRYSTALLINE: This is a type of mineral made of many small crystals.
POST: The pin-like component of an earring that passes through
the pierced earlobe. Usually held in place by a fastening system behind
the lobe, such as the "Butterfly" clasp.
POST AND OMEGA: A hinged fastening clasp that closely resembles
the Greek letter, Omega. Used to secure earring posts to the ear.
PRASIOLITE: Click on
the link and learn everything there is to know about this gem type from
Thaigem.com's extensive resources of information.
Click here for the
on-line catalogue of this gem type.
PRECIOUS METAL: The three primary precious metals are gold,
silver, and platinum. All others (except derivatives of these three)
are known technically as base metals. Of course, the preciousness of
precious metals varies, as does the baseness of base metals. Please
refer to the
Precious Metals Buyer's Guide
for more information.
PREHNITE: Click on
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Thaigem.com's extensive resources of information.
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PRIMARY DEPOSIT: Material still in its host rock.
 PRISMATIC:
Habit in which parallel pairs of rectangular faces form prisms.
PRONG SETTING: This is the most frequently used method of setting
gems into jewelry. Small metal claws with a vice-like grip are bent over
the girdle of the gem to ensure its secure and enduring position in the
ring. Please refer to the
Jewelry Setting Buyer's Guide for
more information.
PURITY: The proportion of precious metal versus base metal in an
object. A purity of .900 would mean a metal content of 90% metal and
10% base metal alloy, or a ratio of 9 to 1. Please refer to the
Precious Metals Buyer's Guide for
more information.
PYRITE: Click on the
link and learn everything there is to know about this gem type from Thaigem.com's
extensive resources of information.
Click here for the on-line catalogue of this gem type.
QUARTZ: Click on the link and learn everything there is to know about this gem
type from Thaigem.com's extensive resources of information.
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catalogue of this gem type.
REFRACTION: The bending of light as it passes from the air into
another medium.
REFRACTIVE INDEX (RI): 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).
This 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 (RI).
REFRACTOMETER: An apparatus used to measure the refractive index
of gemstones.
REGARD: A sentimental piece of jewelry containing six gemstones,
in which the first letter of each gemstone spells the word regard.
R =
ruby,
E = emerald,
G = garnet, A = amethyst,
R = ruby and D = diamond.
RHODOCHROSITE: Click on the link and learn everything there is
to know about this gem type from Thaigem.com's extensive resources of
information.
Click here
for the on-line catalogue of this gem type.
ROCK: Refers to a material that is made up of one or more minerals.
ROLLED GOLD: A base metal alloy bonded to a "veneer" of
precious metal, usually 10 Karat. Please refer to the
Precious Metals Buyer's Guide
for more information.
ROPE: A style of chain in which the links are intertwined to resemble
a length of rope.
ROSE GOLD: Mostly alloyed with copper, this increasingly
popular gold type has a striking pink to reddish hue. Please refer to
the
Precious Metals Buyer's Guide
for more information.
ROUGH: Refers to a rock or crystal still in its natural state before
cutting or polishing.
RUBELLITE: Click on the link and learn everything there is to know
about this gem type from Thaigem.com's extensive resources of information.
Click here
for the on-line catalogue of this gem type.
RUBY: Click on the link and learn everything there is to know about
this gem type from Thaigem.com's extensive resources of information.
Click here
for the on-line catalogue of this gem type.
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