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Guides and Charts
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Nacre
Nacre is a silky substance secreted over a forming pearl. Layer after layer of nacre build up to form what we call a pearl. When light touches the pearl, it travels through all the layers of nacre, and each tiny crystal reflects the light like miniature prisms. The end result? A lustrous, breathtaking pearl.
Natural Pearl
A pearl formed through a process of a mollusk secreting nacre around an irritant that enters the shell naturally without artificial insertion. (See pearl.)
Nephrite
The original jade treasured by the Chinese culture, nephrite is a calcium magnesium silicate and comes in a range of colors from white to green. The composition of nephrite is fibrous, making it one of the “toughest” materials on earth.
Nucleus
A nucleus is the implant (the bead or mantle tissue) inserted into a mussel to create a cultured pearl.
Nugget
A lump of unshaped precious metal. |
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Oiling
Oiling infuses colorless oils, resins and waxes into tiny surface-breaking fissures to hide them and give gems a clean-complexioned appearance. This long-practiced clarity enhancement is used mainly for emerald and jade. The oils used are either natural or have a natural counterpart. If coloring agents are added to the oil, the stones are classified as dyed. Emeralds infused with man-made substances like plastics and polymers that have no natural counterpart are considered impregnated. For a list of stone treatments, frequency and stability of treatments, and care instructions, visit our Gemstone Enhancements and Treatments chart.
Olivine
Olivine is a mineral family containing the gemstone peridot.
Omega Back
An earring closure for pierced ears that is secured by a hinged lever attached to the back of the earrings. Similar to lever back earrings, omega back earrings end in an O shape that secures over a post instead of a clutch.
Omega Chain
Treasured for its sleek sophistication, an omega chain is worn high on the neck and made up of tightly interlocking links that form a flat solid surface.
Opal
Opal is a unique gemstone with a beautiful play-of-color display. It exhibits all colors and both light and dark base colors reflect a rainbow-like display of multiple colors when viewed from different angles. On Mohs’ scale of hardness, opal is 5.5-6.5. Primary sources include Australia, Brazil, Guatemala, Honduras, Indonesia, Japan, Mexico, Russia, Nevada and Idaho.
Opaque
There are several ways a light travels through a stone. In opaque stones, no light is reflected. (See also translucent and transparent.)
Open Work
Similar to filigree, this ring setting is designed to allow viewing of the bottom of the gemstone.
Opera
Ideal for formal engagements, this necklace style drapes elegantly at 28 to 34 inches long. Sometimes it is also doubled and worn as a shorter necklace.
Optical Properties
One fundamental characteristic of gemstones is the way they interact with the light. “Optical properties” refers to this trait and include color, dispersion and fluorescence.
Organic Gemstones
While most gemstones are minerals with an inner structure that result in crystal forms, a few gemstones known as organic gemstones (such as amber and pearl) are primarily non-mineral, being formed by plants and animals.
Orient
The layers of nacre that form a pearl contain tiny light-reflecting crystal. When there enough layers of crystals and they align in a certain way, the reflected light will form a prismatic effect on the surface of the pearl. The beautiful rainbow-like effect is known as “orient.”
Oval Cut
This popular cut is oblong and faceted with rounded edges.
Overlay
There are two techniques of physically joining two materials together: one is inlay and the other is overlay (or encrustation). Overlay unites one surface onto another surface chemically through an additional substance such as soldering when joining metal to metal or an adhesive/cement when joining metal to nonmetal (such as gemstones or shell).
Oxidation
Tarnishing is the natural process of discoloration that occurs in some metals due to environmental conditions. When this change is induced by choice to create a special effect in the metal, it is known as oxidation. |
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Padparadscha
Literally meaning “lotus flower,” padparadscha refers to a lush pink and orange sapphire. Also, the most valuable topaz is pink to reddish orange and is called “padparadscha topaz.”
Pave Setting
This unique setting looks as if the piece is literally paved with stones.
Pavilion
A faceted stone can be divided into an upper and lower section. The upper section or top is referred to as a crown. The lower section is referred to as a pavilion. The perimeter where both parts meet is referred to as a girdle. The flat plane on top of the stone is called a table, and the bottom point (when present) is referred to as a culet.
Pear Cut
Resembling a pear or teardrop, this fancy cut is rounded on one end and pointed on the other.
Pearl
A pearl is a lustrous, organic gem produced by saltwater oysters, freshwater mussels and occasionally by some shellfish. It exhibits a range of colors from white to pink, silver, cream, peach, gold, green, blue and black. Oh Mohs’ scale of hardness, pearl is 2.5 – 4.5. Primary sources of Sea Pearls include Persian Gulf; Gulf of Manaar; along the coasts of Madagascar, Burma (Myanmar), and the Philippines; many islands in the South Pacific, northern Australia; and the coastal lines of Central and northern South America; and some small beds in Japan. Primary sources of freshwater Pearls include United States, some in Europe (restricted in Central Europe).
Pendant
An ornament that hangs from a necklace or bracelet is known as a pendant.
Perfect Cleavage
See cleavage.
Peridot
Peridot is a gemstone in the Olivine mineral family. It exhibits a range of vibrant greens from yellow-green to olive green to brownish green. On the Mohs’ scale of hardness, peridot is 6.5-7. It displays a vitreous and oily luster and the primary sources include Burma (Myanmar), Australia (Queensland), Brazil (Minas Gerais), China, Kenya, Mexico, Pakistan, Sri Lanka, South Africa, Tanzania, and Arizona.
Petalite
Petalite is primarily a gemstone for collectors. It is often colorless but there are also examples of pink and yellow varieties. On the Mohs’ scale of hardness, petalite is 6-6.5. It has a vitreous luster and sources include Western Australia, Brazil (Minas Gerais), Italy (Elba), Namibia, Sweden, Zimbabwe, and the United States.
Pewter
This dull silver-colored alloy is made from tin, antimony and copper.
Phenomenal Gems
Gems that display unusual optical properties such as color change gems.
Play of Color
Opal displays a burst of striking colors known as play of color. As the stone is moved, the appearance changes and a different display of rainbow-like colors can be seen from different angles. This play-of-color is caused by the diffraction of light hitting the stone. In the 1960s, intensive microscopes magnifying between 20,000x and 40,000x revealed that tiny silica spheres (150 to 300 nanometers) with water interspersed make up opals. The shape, size, and alignment of these spheres affect the color of the opal.
Pigeon’s Blood
While rubies come in a variety of red tones, the most valued color is pure red with a hint of blue, known as “pigeon’s blood” red.
Platinum
Thirty-five times rarer than gold, platinum is a treasured and highly sought after precious metal. Platinum is 95% pure, reflecting a brilliant white luster that does not fade or tarnish. Its purity also makes it hypoallergenic and perfect for sensitive skin. With a higher density than most metals, platinum is more durable and less likely to wear away over time. Plus, it is highly pliable and can be shaped into many intricate patterns not possible with other metals.
Pleochroism
In a doubly refractive crystal, a light beam reflects two different rays. The eye cannot normally see both rays at the same time, but by moving the stone, the eye will observe both rays. The result? The stone exhibits one of two or more different colors (or two or more different color depths) from each angle. This effect is known as dichroism (two-color) or the more common pleochroism (many colors). Tourmaline is a perfect example.)
Plum Gold
Karat gold with the exact amount of stated gold content.
Point
Gemstone unit weight equal to one-hundredth of a carat.
Polish
Polish is a finishing process for metals and gemstones. There are several methods of polishing, depending on what is being polished. (See "Polishing Metals", "Polishing Diamonds" and "Polishing Gemstones".)
Polishing Diamonds
Finishing diamonds is the art and science of a lapidary. For cutting and polishing, the diamond is mounted and pressed into a rotating grinding wheel coated with diamond powder and oil. Polishing diamonds requires constant inspection to make sure all the facets are symmetrical and uniform.
Polishing Gemstones
While cutting and polishing a diamond incorporates mathematical formulas, the art of cutting and polishing gemstones is more dependent on experience and experimentation of the lapidary. Once the stone is sawed and ground into the desired shape, it must be sanded to remove rough marks and then it is polished with a variety of agents. Depending on the stone hardness and the type of facets, the gemcutter will combine a variety of polishing agents and polishing surfaces to finish the stone into brilliant shine.
Polishing Metals
In the art of crafting metals into jewelry, the last step involves refining the surface to a beautiful bright finish. This process includes both polishing and buffing.
Polishing involves a multi-step process of hand polishing and/or machine polishing. This phase eliminates all flaws from the surface of the metal. This may take several stages of polishing using multiple abrasives, tools and techniques.
Buffing utilizes much finer abrasives and removes very little, if any, metal. This step brings the metal to a final finish with a varying degree of brightness depending on the tastes of the jeweler.
Princess
Perfect for every occasion, this necklace style ranges from 17 to 19 inches and looks great on high and low necklines.
Prong
A prong is a small, slender metal piece. Several prongs connect to a bezel or base and are used to hold a stone in place.
Proportion
Proportion is the property of the relationships between the angles and measurements on a polished gem.
Pyrite
Natural pyrite has a brassy appearance and it sometimes confused for gold. It has little or no gold content and is often called “fool’s gold.” Used by jewelers for thousands of years, pyrite has been found in ancient Greek jewelry and the tombs of Incas. Marcasite jewelry is actually pyrite.
Pyrope
Pyrope is a variety of garnet. It usually exhibits a blood-red color but can also be tinged with yellow or purple. On Mohs’ scale of hardness, pyrope is 7-7.5. It has a vitreous luster and primary sources include Burma (Myanmar), China, Madagascar, Sri Lanka, South Africa, Tanzania, and the United States. |
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Quartz
Quartz is one of the most common gem families and can be found all around the world. Quartz comprises several different groups of gems from crystalline quartz (crystals viewable by the naked eye) and crypto-crystalline (microscopic crystals). Crystalline quartz includes amethyst, aventurine, rock crystal, blue quartz, citrine, hawk’s eye, prasiolite, quartz cat’s eye, smoky quartz, rose quartz, and tiger’s eye. Crypto-crystalline quartz is also known as chalcedony and includes agate, bloodstone, carnelian, chyrsoprase, jasper, moss agate, onyx and sard.
Quartz Movement
Quartz movement is a very accurate method of movement powered by the vibrations of tiny quartz crystals. |
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