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Guides and Charts
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Half-Hoop Design
Also known as demi-hoop design, this earring looks like its name, forming only half a circle.
Hammered
A dimpled surface treatment created by a small hammer.
Hardness
See Mohs’ hardness scale.
Head
Head refers to the prongs that hold a stone in place on a setting.
Head Shape
The shape on the face of a ring is determined by the shape of the gemstone set in it.
Head Size Range
Head size range is the range of carat weight that a ring can mount in one specific head.
Heating
Heating is an ancient and normally stable enhancement that permanently transforms gems. Gemologists use low, medium and high temperatures in furnaces to alter gemstone color, clarity and phenomena. Nearly all of the world’s ruby, sapphire and tanzanite owe their color and clarity to heating. Many aquamarines are also heated to eliminate traces of green and gray. For a list of stone treatments, frequency and stability of treatments, and care instructions, visit our Gemstone Enhancements and Treatments chart.
Heishi
Literally meaning, “shell,” heishi (hee shee) is considered the most ancient jewelry form of New Mexico and is linked to the Santo Domingo and San Felipe Pueblo Indians. Heishi originally referred to pieces of shell exquisitely crafted and strung on necklaces. Now it may also refer to small hand-made beads of other materials.
Herringbone
A herringbone chain has small, slanted links that join to form a flat chain.
Hessonite
Hessonite is a brown red variety of garnet.
Hidden Box Clasp
This stylish design hides a box clasp under the last link of the chain.
High Polish
Mirror-like finish of a highly polished piece of jewelry.
Hoop Earring
This refers to an earring in the shape of a hoop.
Hue
Hue is one of three characteristics used to describe the appearance of color. Hue is the dominant wavelength of color attributed to a particular stone. |
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I.D. Bracelet
This bracelet, with a curved plate, displays the name or initials of the wearer.
Igneous
Deep within the earth’s inferno is a stew of molten rock and gases, called magma. As magma wells up within the earth, intense pressure forces the liquid rock toward the earth’s surface. It is referred to as lava when it breaks through the surface. Lava slowly cools forming igneous rocks, and within these rocks and gas-bubble spaces, interlocking crystals grow. The minerals present, the cooling time and the environment will all play a role in the way these crystals form. Examples of gemstones found in igneous rock: diamonds, topaz, kunzite and spinel.
Inclusion
Inclusions are foreign deposits within gemstones such as foreign minerals, cracks, or liquids. They occur naturally during crystal growth and may also result from intense pressure. Some inclusions are visible to the naked eye and some can only be seen with a loupe. While they sometimes affect the appearance of a stone, they can also help verify authenticity and reveal stone origins.
Indicolite
See tourmaline.
Inlay
Inlaying is a decorative technique of binding one surface into the surface of another material mechanically (by incision and undercut). (Also see overlay.)
Intaglio
An Intaglio is an ornamental stone with a design formed into the stone, sitting below the surface. (In contrast with a cameo.)
Intarsia
Also known as Florentine Mosaic, Intarsia is an art form created by cutting various gemstones together in a pattern. It originally referred to inlay of wood veneers, ivory, or metal into a wood ground.
Intensity
See saturation.
Iolite
Iolite is a gemstone with a slight variability in chemical composition between stones. It exhibits a blue-to-violet range of colors and sometimes shows a brownish streak. On Mohs’ scale of hardness, iolite is 7-7.5. It has a greasy luster and primary sources include Burma (Myanmar), Brazil, India, Madagascar, Sri Lanka and the United States.
Iridescent
A rainbow range of colors reflected from the surface of a gemstone.
Irradiation
A gemstone enhancement process, irradiation uses high energy, sometimes followed by heating, to alter gemstone color. Diamonds are sometimes irradiated to produce or enhance various colors. Other gemstones may also be treated using this method. For a list of stone treatments, frequency and stability of treatments, and care instructions, visit our Gemstone Enhancements and Treatments chart.
Irritant
Key to the formation of pearls, an irritant is any intruder such as a parasite or particle that gets inside a mollusk’s shell. The mollusk produces a secretion known as conchiolin to soothe the irritant. Another substance known as nacre is secreted over the conchilin. Layer after layer of nacre surrounds the irritant and eventually produces what we know as a pearl. |
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J Hoop
A hoop earring that is not circular but elongated like the letter “j.”
Jade
Called the stone of heaven, jade is a hard stone that has been treasured by the Chinese for over 7,000 years. Jade actually comes from two different mineral species with similar appearance: nephrite and jadeite.
Jadeite
Jadeite is a sodium aluminum silicate and has become the most popular form of jade. It comes in a variety of colors from the popular greens to orange, yellow, brown, blue, purple and black. On Mohs’ scale of hardness, jadeite is 6.5-7. It has a greasy luster and primary sources include Burma (Myanmar), China, Japan, Canada, Guatemala, Kazakhstan, Russia (Siberia), and California. |
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Karat
Karat is a measure of the gold’s purity. Most gold jewelry is actually made from a gold alloy containing gold and another metal or metals. (See 10 karat, 12 karat, 14 karat, 18 karat and 24 karat.)
Kunzite
Kunzite is a variety of the Spodumene family. It is known for a range of pink-violet to light-violet colors but has also been identified in canary yellow, colorless, brown and green-violet. On Mohs’ scale of hardness, kunzite is 6.5-7. It has a vitreous luster and its sources include Brazil (Minas Gerais), Afghanistan, Burma (Myanmar), Madagascar, Pakistan and the United States.
Kyanite
Kyanite has a similar chemical composition to andalusite and fibrolite but it has a different crystal structure. It exhibits a range of colors including blue to colorless, blue-green and brown. On Mohs’ scale of hardness, kyanite is 4 – 4.5. It has a vitreous luster and primary sources includes Burma (Myanmar), Brazil, Kenya, Austria, Switzerland, Zimbabwe and the United States. |
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Lab Created
Gemstones created in a lab with exact chemical properties of their natural counterparts are termed lab created. Also known as synthetic stones, these stones are usually significantly cheaper than natural stones.
Labradorite
Labradorite is a gemstone in the feldspar family. It is known for a brilliant play of color and exhibits lustrous metallic tints of blue, green, yellow, red, gold and purple. On Mohs’ scale of hardness, labradorite is 6 – 6.5. It has a vitreous luster and primary sources include Canada (Labrador, Newfoundland), Australia (New South Wales), Madagascar, Mexico, Russia and the United States.
Lapidary
Lapidary is the art and science of cutting, polishing and shaping precious gemstones.
Lapis Lazuli
Lapis Lazuli is a complex composition of multiple minerals. It exhibits a range of beautiful blues from lazur blue to violet to greenish blue. On Mohs’ scale of hardness, lapis lazuli is 5-6. It has a vitreous and greasy luster and primary sources include Chile, Russia, Afghanistan, Angola, Burma (Myanmar), Canada, Pakistan, California and Colorado.
Lariat
A cord necklace with two open ends handing down in front, looped into a knot or secured by a slide.
Lever Back
An earring closure for pierced ears that is secured by a hinged lever attached to the back of the earring.
Links
Links are the loops or other shapes that connect together to form a chain.
Lobster Claw Clasp
This necklace or bracelet clasp uses a hook similar to a hinged lobster claw to secure one end to a ring on the other end of the chain.
Luster
The quality and quantity of light reflected by a stone’s surface. Luster can also refer to the unique glow that emanates from a pearl as a result of the microscopic crystals in the nacre of the pearl. |
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Mabe' (Or Mobe') Pearl
A dome shaped pearl that is normally round or tear shaped but also comes in a variety of shapes and sizes. The mabe is assembled by placing a small half sphere object against the shell of an oyster. After the oyster coats this irritant with nacre, the new pearl is cut from the oyster. The flat side of this new pearl is hollow and filled with epoxy and then covered with mother of pearl. Mobe pearls are a great way to get a large pearl for a lower price, but they are fragile and require special care.
Maltese Cross
A cross made up of four arrowheads facing one another with their points meeting in the center.
Mantle
Mantle tissue is the soft tissue found in an oyster and is the medium for the cells that start the production of conchiolin and nacre. In cultured pearls, a round bead is inserted into the oyster with a piece of mantle tissue. In the unique irregular shaped freshwater cultured pearls, mantle tissue alone is implanted into the oyster. These are known as “tissue graft” or “non-nucleated” cultured pearls.
Marcasite
Marcasite jewelry is actually pyrite. The minerals marcasite and pyrite are similar in composition but they crystallize differently. True marcasite is unsuitable for jewelry. The confusion between the two dates back several hundreds years due to the confusion between pyrite and marcasite based on their similarities. Marcasite jewelry (pyrite) is a popular style that became fashionable during Queen Victoria’s reign. Marcasite jewelry normally uses pyrites cut and polished in circular outline and mounted in a rhodium-plated silver setting.
Mariner Link Chain
A chain made of oval links that have a bar across the center.
Marquise
Named after Marquise de Pompadour, Mistress of King Louis XV, the marquise shape is oval with points on both ends.
Matched Pair
Two matching gemstones perfect for use in earrings.
Matinee
This necklace style that ranges from 20 to 25 inches long and is perfect for semi-formal occasions
Matte
A dull, non-reflective finish.
Metal
In one sense, jewelry is the art and science of crafting metals. Regardless of whether gemstones are present or not, virtually all jewelry incorporates some form of metal. Even bead and pearl necklaces normally incorporate some form of metalwork in the clasp. While 70 pure metals exist, only about 20 are used in the craft of jewelry making. Under controlled conditions (such as heating) metals are malleable and can be shaped into various designs. At room temperature, metals are solid and opaque.
Metallic
Reflective like metal.
Mill Grain Edge
Created with a special engraving tool, a millgrain edge is a raised design along the edge of the jewelry.
Mineral Crystal
Most gemstones are actually mineral crystals (except for non-mineral gems like pearls, coral and amber). Mineral crystals form through a naturally occurring combination of chemicals, heat and/or pressure. These chemicals affect shapes and color of the crystals. Most mineral crystals are tiny, but a few can be cut into gemstones of rare beauty.
Mohs' Hardness Scale
The common standard for rating gemstone hardness is Mohs’ scale. Friedrich Mohs, a German mineralogist, developed an assessment of “scratch hardness” by ranking 10 different stones from hardest to softest. His list includes the following:
10. Diamond (Hardest)
9. Sapphire
8. Topaz
7. Quartz
6. Orthoclase Feldspar
5. Apatite
4. Fluorspar
3. Calcite
2. Gypsum
1. Talc (Softest)
Because these numbers are based on actual stones, they are not equally distributed, so, for example, the difference between 10 (diamond) and 9 (sapphire) is greater than the difference between any other set of numbers. Softer stones scratch more easily and some stones are simply too soft for jewelry. See our Gemstone Enhancements and Treatments chart for a comprehensive list of stones including their Mohs’ hardness. Note: hardness is not the only determination for durability, also see cleavage.
Moissanite
Moissanite is a lab-created stone based on the structure of natural moissanite, which is linked to meteorites. On Mohs’ scale of hardness, moissanite is 95. It has more brilliance, fire and luster than any hard jewel on earth, including diamond.
Moldavite
Moldavite is part of the tekite group. It exhibits a bottle-green to brown-green color. On Mohs’ scale of hardness, moldavite is 5.5. It has a vitreous luster and primary sources include Australia (Australite), Borneo (Billitonite), Georgia, United States (Georgiaite), Indochina (Inchinite), Java (Javaite), and the Philippines (Philippinite).
Mollusk (mollusk or mollusc)
A mollusk is an animal with a soft body and an external skeleton or shell. The shell protects and supports this fragile animal. There are over 100,000 species of mollusks on the planet, but only a few produce the wondrous beauty of pearls.
Moonstone
Moonstone is a gemstone in the Feldspar family. It exhibits a range of colors including yellow, a pale silver sheen, a blue and even pink. On Mohs’ scale of hardness, moonstone is 6-6.5. It has a vitreous luster and primary sources include Sri Lanka, Burma (Myanmar), Brazil, India, Madagascar and the United States.
Morganite
Morganite is a gemstone in the Beryl family. It exhibits a range of colors from soft pink to violet to salmon. On Mohs’ scale of hardness, morganite is 7.5-8. It has a vitreous luster and primary sources include Afghanistan, Brazil, China, Madagascar, Mozambique, Namibia, Zimbabwe and the United States (California, Utah).
Mother of Pearl
“Mother of pearl” is the pearl lining of an oyster. Only mollusks that have this lining can produce pearls. This lining is also used as inlay in jewelry and other ornamental items.
Mounting
A piece of jewelry designed to hold a gem. |
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