AZGem Gems
September, 2009

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The World's Most Useful
Gem & Jewelry Monthly Newsletter

Written by Carolyn Doyle for customers of
The Dorado Company
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Usable Gems... and a little opinion.


Gemstone and Diamond  Dictionary


 gemstone and diamond dictionary


This Gemstone and Diamond Dictionary is presented by request. While there are several gem-focused glossaries or dictionaries available on the internet, I have been requested to add my version to this site for your convenience.

This list has been compiled by looking at definitions on other dictionaries and glossaries. Where I judged a definition to be unclear, geared too much toward marketing, or otherwise lacking, I have edited that definition.

I have done so sparingly, to promote standard definitions.

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 



Refers to the diamond-like luster of a gemstone. Gemstones with a diamond-like luster include diamond (of course), demantoid garnet and sphene

The appearance of a floating, billowy light in cabochon gemstones or a stationary sheen on the flat surface of a gemstone. Seen in certain Feldspars such as Moonstone. Schiller.

Alluvial Deposits
Gem deposits found in water after they have been separated from the mother rock.

Altered Stone
Any stone that has been changed in appearance, particularly in color, by an artificial process. Also referred to as an Enhanced Gemstone or a Treated Gemstone. Heating, irradiation, and dyeing are among the processes used to change gemstone appearance.

The color violet to purple in a gemstone..

Gemstones without a crystal structure are referred to as amorphous. These include gems such as amber, coral, opal and pearl

Angle of Incidence
The angle at which a ray of light enters a stone as measured from normal.

Angle of Reflection
The angle at which a reflected ray of light leaves a surface as measured from normal.

Angle of Refraction
The angle at which a reflected ray of light leaves a surface as measured from normal.

Term used in gemology for double refraction.

Artificial Stone
A man-made, imitation of a gem. Neither a natural nor synthetic gem.

The appearance of a rayed figure or rayed star in a gemstone, caused by the reflection of light from minute inclusions. Star Sapphires and Star Rubies are two well-known examples of gemstones featuring a rayed star.

A glittery appearance of the surface of a gemstone, caused by the reflection of light off small mineral inclusions. Aventurine Quartz and Goldstone (glass) both have aventurescence.  


Balas Ruby
Trade name for Red Spinel.

Rectangular style of step cut used for small gem materials.

May apply to certain gemstones or pearls. Either a gemstone or pearl with an irregular shape, such as Tumbled Stones or Baroque Pearls.

The pavilion (The portion of a facetted gemstone below the Girdle.)

The English name for the Baguette cut.

A hollow gemstone, usually round. Designed to be strung.

Bead Setting
A method of securing a facetted stone. A small burr of metal is raised with a graver and worked to the edge of the stone. This burr is then burnished with a concave tipped punch into a small ball over the girdle of the stone. Normally used to secure very small gemstones, usually in multiples.

The supporting ledge of a stone setting.

Beryllium Treatment
A form of heat treatment for sapphire that adds the element beryllium to the heating process. Beryllium is an element well known in the gem world, since it is an essential constituent in many gemstones, including emerald, beryl, and aquamarine. When sapphires are heated with beryllium, the result is a reduction in blue tones. Thus bright yellow or orange sapphire can be produced from weak yellow or greenish gems. Some stunning colors have been produced using this method.

Emerald, aquamarine and other aluminum beryllium silicate minerals.

A thin strip of metal that holds a gemstone in place. Used in place of prongs.

A double-refractive gemstone, which has two directions of single refraction or optic axes.

A gemstone exhibiting two color zones, such as ametrine or many tourmalines.

The numerical measurement of double refraction in gemstones.

The association of gemstones with astrology goes back centuries. More recently,

An on the surface of a gemstone. For example, on a diamond, one would be referring to a nick, knot, scratch, abrasion, minor crack or fissure (cavity), or a poor polish.

According to the Federal Trade Commission, only diamonds with a distinct blue body color may be traded as "blue-white."  For many years the term referred to a diamond without a distinctive body color, however misuses of this term have rendered it almost meaningless.

The process of placing the facets on a stone.

Body Appearance
The optical characteristic of a gem produced by internal inclusions, fractures or layers.

Body Color
The dominant hue within a gemstone.

Box Setting
A method of stone setting in which the gem is enclosed in a box and the edges of the metal are pressed down to secure the stone.

The total amount of white light returned to the viewer by a gem. This includes internal and external reflections.

Brilliant Cut
The most common style of diamond cutting, also used for many other gemstones, which consists of a combination of triangular and kite shaped facets. The round brilliant cut features 57 or 58 facets.

Bristol Stone/Bristol Diamond
Old trade-term for colorless crystal quartz. Also a trade name for colored glass immitations, Bristol Glass or Bristows.

A method of rough-diamond fashioning by rubbing one diamond against another.


A gemstone with a domed form. The oldest form of gem cutting.

Many gemstones are sold in calibrated or standard sizes that will fit commercial jewelry settings. Standard sizes are calibrated in millimeters for a number of different gem shapes.

Calibre Cut
Gemstones cut to a specific, standardized size for mounting. Also, small gem material cut for pave' setting.

A gem or shell material--usually with two or more distinct colored layers. The top layer is carved in relief and the bottom layer acts as a contrasting background.

A term referring to diamonds with an intense yellow hue. The term "fancy yellow" is often used if the yellow makes the stone very distinctive.

A unit of weight measure for gems.

Carbon Spots
Any black-appearing inclusions in a diamond caused by the of other mineral crystals, such as garnet.

Cat's Eye
A gemstone that displays a thin band of reflected light on its surface when cut as a cabochon. Chatoyancy.

The appearance of well-defined bands or The appearance of well-defined bands or threads of light across the surface of a gemstone.  

Center Stone
The center stone is the prominent center piece in a jewelry setting that has multiple gemstones. See also Side Stone.

Change of Color
A phenomenon seen in some gems which have a different color in natural light than in artificial light. The color-change is caused by selective absorption and transmission of light. Alexandrite has become a very well known color-change gem, but other gemstones may exhibit the phenomenon.

The city in southeastern Thailand famous as one of the world centers for gemstone processing and trading. Chanthaburi is also famous for its weekend gemstone market.

The appearance of well-defined bands or threads of light across the surface of a gemstone. This appearance is caused by the reflection of light off small parallel mineral inclusions. May appear as a single-band chatoyancy--Cat's Eye--or a series of bands--Tiger's Eye.

The tendency of Opals to crack when exposed to heat or drying air. Also known as Crazing.

A gemstone with a smooth concave depression.

A popular, common name for a small rose-cut or single-cut gemstone.

Referring to a stone's lack of inclusions or other visual defects.

Clarity Grade
One of the 4 C's. Grades range from F (flawless) through several grades of I (included).

Claw Setting
A stone setting of projecting metal claws which grip the stone at--and just above--the girdle.

A trade term for gemstones which are free of noticeable flaws.

A smooth, flat break or separation in a gem along the direction of its atomic structure.

A group of small, white inclusions that give a cloudy appearance to a diamond.

Cluster Setting
Closely set gemstones arranged to give the illusion of a single, larger gemstone.

Coated Stone
A gemstone covered by an artificially applied transparent material to enhance its color. Often used with Topaz.

The removal of undesired material from a piece of gem rough.

Collet Set
A variation on box setting in which the sides of the box are filed away to sallow more light to enter the gemstone.

Used in the evaluation of a gem. The quality of a gem can based on either the presence or the absence of color.

Color Change Gems
Color change gems change color due to changing light conditions (such as alexandrite or color change sapphire) or when viewed from different angles (such as andalusite or iolite).

Color Grade
One of the 4 c's. Diamonds are ranked on a scale from "D" (colorless) to "Z" (noticeable tint of color, typically yellow or brown). Diamonds with saturation greater than "Z" color are considered Fancy Colored Diamonds and are graded on a separate scale.

Color Zoning
Uneven color in gemstones in irregular patches. Can be either different colors or different tones of the same color.

Colored Stones
A gemstone other than a diamond.

Concave Cut
Traditional gem facets are fla.. Concave cutting creates facets that are curved or scooped. These curved facets refract more of the ambient light and return it to the eye as brilliance. Concave cutting is a recent innovation dating back to the early 1990's. It requires considerable expertise and results in higher weight loss to the rough stone, since more material must be cut away to create the curved facets.

Gemstones that contain traces of copper are very rare and typically have a intense blue, blue-green or violet color. There was considerable excitement in the gem world when the first copper-bearing gemstones were discovered in 1989. See also Paraiba.

Sapphire and ruby. A crystalline form of aluminum oxide.. It is naturally clear, but can have different colors when impurities are present. Corundum is much admired for its hardness (9.0 on the Mohs scale) and brilliance and excellent wearability.

The tendency of Opals to crack when exposed to heat or drying air. Also known as Checking.

Critical Angle
Greatest angle measured from normal at which light can be refracted out of a stone. Small angle at which light is totally internally reflected.

The part of a facetted gemstone above the girdle.

Crown Setting
A collet setting consisting off a flared cylinder with one end of the cylinder notched to form prongs.

Extremely small crystals which cannot be seen separately, even under high magnification.

A solid made up of atoms, bounded by natural planar surfaces.

Crystal System
The classification of minerals according to the geometric form in which their crystals grow. Each mineral has a distinct system--Isometric, Tetragonal, Hexagonal, Orthorhombic, Monoclinic and Triclinic.

Having a regular crystal structure.

The science of the internal structure of crystals.

Cubic System
The Isometric crystal system which consists of three axes, each of equal length and perpendicular to others.

Cubic zirconia
A lab created diamond simulant, often abbreviated as CZ. While CZ is a transparent stone, trace elements can be added to the manufacturing process, producing a wide range of colors. On Mohs scale of hardness, CZ is harder than other gemstones except for diamond, ruby, sapphire and chrysoberyl. Not to be confused with Zircon, a natural gemstone.

A small polished surface placed at what would be the point or ridge of a facetted stone, used to reduce chipping.

Copper bearing.

One of the 4 C's. The angles and proportions of a gem. The placement of facets. Example - round brilliant cut.

gemstone and diamond dictionary

A raised relief carved into a gemstone in a concave depression.


a rare and valuable andradite garnet. It exhibits a range of greens from dull to bright emerald green and on rare occasions displays yellow. On Mohs scale of hardness, demantoid is relatively soft at 6.5. It has an adamantine luster.

Mass per unit volume. The amount of matter in a given space. The higher density/atomic mass of a gemstone, the more it weighs for a given size.

An early term for glass imitation stone without foil backing.

A mineral that crystallizes in the cubic system and is composed of carbon with a hardness of 10, a refractive index of 2.417, and a specific gravity of 3.52. 

Diamond Cut
Also known as the round Brilliant Cut, the style of cutting a stone with multiple facets to maximize brilliance. Modern round brilliant cuts have 58 facets.

The transmission of two different colors in two different optical planes as light passes through a gemstone. May be used as a method of distinguishing one type of gemstone from another.

An instrument used to view the light passing through a gemstone to determine the presence of dichroism.

Diffusion Treatment
A form of heat treatment that adds one or more chemicals to the heating process to change the color of a gemstone. Typically the treatment does not penetrate deep into the stone, so gems treated in this way cannot be recut. Diffusion treatment is a standard treatment to increase the asterism effect in star sapphire.

The separation of light into its spectral colors as it passes through a gemstone.

A twelve-sided geometric solid. One of the crystal forms found in the Isometric crystal system.

Double Refraction
The separation of a beam of light into two separate beams as it enters a gemstone. The two beams travel at different speeds. May be used to distinguish one gemstone material from another. Occurs in all crystal systems except Isometric.

An assembled stone of two parts. Colorless cement or heat is used to join the parts together. Often used with Opals.

The combined characteristics of hardness, toughness and stability in gemstones. One of the deciding factors in gemstone value.

Dyed Stone
A gemstone to which an artificial stain is added to improve color or to imitate a more valuable gemstone.


Eye Clean
Refers to a gemstone that appears to have no visible inclusions or imperfections to the naked eye. Compare Loupe Clean.


The plane surfaces which form the sides of a crystal.

A planar surface which is polished onto a gemstone.

Fancy Cut/Fancy Shape
Any style of gemstone cutting other than the round brilliant or single cut.

Fancy Diamond
Any diamond with a body color strong enough to be attractive.

A trade term referring to any inclusion within a gem, usually a jagged irregular fracture which appears white.

Fingerprint Inclusion
Liquid and/or gas or solid flaws in gemstones which align in the form of a human fingerprint.

The quality of a prepared surface. In facetted gemstones, the placing of the facets and the quality of polish. In cabochon gemstones, the quality of the polish.

The play of color on or within a gemstone as a result of dispersion. Prominent valued feature of Opals and Fire Agates.

A surface crack on a gemstone. Gems with fissures may be Fracture Filled.

Any visible imperfection within a gemstone.

The emission of visible light when a gemstone is exposed to ultraviolet light. Used a method of distinguishing one gemstone from another and a natural gemstone from a synthetic gemstone.

Foil Backed
The adding of a layer of metallic foil to the back of a gemstone to improve its color or brilliancy.

A break or chip in a gemstone in any direction other than along a cleavage plane.

Fracture Filling
Applying a material that will allow the light to pass through smoothly. Different materials are used; oil, wax, glass, epoxy, and borax are common materials. The most commonly filled stones are emerald, turquoise and ruby.

Full Cut
A round-shaped, brilliant-cut gemstone having 58 facets.


A mineral or organic material with sufficient beauty, rarity and durability  to be used as a jewel when cut and polished.

The study of gemstones--identification, grading, appraisal, marketing, and fashioning.

A rock which contains a cavity lined with mineral crystals.

A gemstone with a glowing, milky sheen that moves as the stone is moved in the path of a light source. Opalescence.

The outer edge of a gemstone.

The art of engraving or carving gems.

Greasy (luster)
One of the the technical terms used to refer to the luster of a gemstone. Jadeite is an example of a gem with a greasy luster.

Two or more chemically related gemstone materials, similar in structure and physical properties.

Gypsy Setting
A setting in which the crown of a gem is the only portion exposed and the table of the gemstone is nearly level with the surrounding metal. No prongs or separate bezel is evident; all means of setting the gemstone are below the metal's surface.


The most common form in which a mineral occurs.

A gemstone material's ability to resist scratching.

An added finding to mount a gemstone in a prong setting.

Heating a gemstone material to improve color.

Heavy Liquid
A liquid of known specific gravity, used to test the specific gravity of a gemstone.

Hexagonal System
A crystal system which consists of four axes, three intersect at a 60-degree angle of each other while the fourth is perpendicular to the other three.

the dominant wavelength of color attributed to a gemstone. There are six primary hues: violet, blue, green, yellow, orange, and red. In between these primary hues are secondary hues, such as blue-green. See also tone and saturation


Illusion Setting
A setting in which the surrounding metal's surface is cut or shaped to appear to be part of the gemstone. Technique is often used to enhance the perceived size of small diamonds.

A visible irregularity in a gemstone.

Blue tourmaline. From bright blue hues to bluish green colors, indicolite tourmaline is one of the rarer tourmaline colors.

A design carved into the surface of a gemstone--the opposite in character of a cameo.

The color of a gemstone from bright to dull.

Interference Colors
Colors revealed by a polarisope as polarized light pass through a gemstone. Used to detect the presence of double refractivity in a gemstone.

Spectral colors observed inside or on a gemstone. It is caused by light passing through layers of differing refractive indexes. The colors seen in Opals are a result of iridescence.

Exposing gemstones to radioactive rays for the purpose of changing or enhancing the original color.

Isometric System
The Cubic crystal system which consists of three axes, each of equal length and perpendicular to others.


A gemstone


Karat (as distinguished from Carat) is a measure of the purity of gold. Most gold jewelry is actually made from a gold alloy containing gold and another metal or metals. 18K gold, for example, is 75% pure gold.


Man-made gemstone that has similar physical, optical and chemical properties of a natural gemstone. Also Lab created or synthetic gemstone.

The science and art of cutting and polishing gems to their finished state.

small, high-powered magnifying lens held or worn close to the eye. Used by gemologists, jewelers, watch makers.

Loupe Clean
A gemstone without inclusions or defects visible when the gem is viewed with 10 times magnification. See also Eye Clean.

The appearance of a surface resulting from reflected light. Diamonds exhibit Adamantine Luster, glass and most gemstones exhibit Vitreous Luster, amber exhibits Resinous Luster.


A trade term referring to the quality of a gemstone's cut.

The marquise shape is an elongated oval with points on both ends

The rock in which gemstone material is found. Some matrix material may remain in a finished gemstone--the veining in turquoise is a common matrix seen in a finished gemstone.

Gemstones of approximately .18 carats or less. May refer to all gemstones or cutting styles, but is usually used for round, facetted diamonds.

Metallic (luster)
One of the technical terms used to refer to the luster of a gemstone. A gemstone that is reflective like polished metal is said to have a metallic luster. Hematite is one of the rare examples.

A style of setting in which the stone is held in place by a row of tiny beads along the girdle of the stone.

Inorganic substances occurring naturally and having a definite chemical composition and crystal structure.

The study of minerals, including their physical and chemical properties.

Mixed Cut
A gemstone cut consisting of a brilliant-cut crown and step-cut pavilion.

Moh’s Hardness Scale
A categorization of minerals according to their hardness--resistance to scratching. Diamond is the hardest and talc is the softest. The comparative scale of hardness is
1) talc
2) gypsum
3) calcite
4) fluorite
5) apatite
6) moonstone
7) quartz
8) topaz and beryl
9) corundum
10) diamond

A lab-created diamond simulant based on the structure of natural moissanite. On Mohs' scale of hardness, moissanite is 9.5. It has more brilliance, fire and luster than any hard jewel on earth, including diamond.

Monoclinic System
A crystal system which consists of three axes, each unequal in length with two intersecting at oblique angles and the third perpendicular to the other two.

The portion of a piece of jewelry which holds a gemstone. A setting.


The iridescent substance secreted by a mollusk during the formation of a pearl that consists of layers of aragonite and calcite crystals.

A trade term for a portion of the original surface of a rough diamond left by the cutter when polishing and faceting a diamond. Naturals are usually found near the girdle of a diamond and are represented in green on a plotting diagram.

Natural Gemstone
A gem produced by nature.

NATURAL PEARL - A pearl that originates naturally in a mollusk, as distinguished from cultured or imitation pearls.

NICK - A minor chip on the surface of a diamond, usually found near or on the girdle of the stone

In the study of light, an imaginary line perpendicular to a surface. Used in gemology to describe the angle at which light strikes an object.


An eight-sided geometric solid and one of the forms in the Isometric Crystal System. The most common crystal in which diamonds occur.

The application of colorless oils, resins or waxes into tiny surface-breaking fissures to hide them and give emeralds or gemstones a cleaner appearance

Milky or pearly appearance. Girasol.

The quality of not allowing the transmission of light.

Optic Character
The effect a material has on the transmission on light.

Optical Properties
The behavior of light within a material.

Organic Gem
Naturally occurring substances wholly or partly derived from plants or animals. Amber, coral, jet, pearls.

Oriented Stone
A gemstone cut to place the optical axis, and resulting phenomenon, in proper position--star sapphires and star rubies.

Orthorhombic System
A crystal system which consists of three axes, each unequal in length and intersecting at ninety-degree angles.


Derived from the Sinhalese term for "lotus flower," padparadscha refers to a lush pink and orange sapphire resembling the color of the lotus. Padparadscha is also sometimes used to refer to other types of gemstones, such as topaz and tourmaline, with this unique coloration.

A rare copper-bearing tourmaline with an intense blue or blue-green color, first found in the state of Paraiba in Brazi. There have been recent finds in Nigeria and Mozambique of similar material, and the term "paraiba" is now used to refer to all examples of this copper-bearing tourmaline. See also Copper-bearing.

Flat, smooth breakage of a mineral along planes or twinning, commonly found in corundum.

Glass usually containing lead oxide and cut to simulate a gemstone.

Small stones set in the surface of metal as close together as possible.

The portion of a facetted gemstone below the girdle.

Pear Shape
Resembling a pear or teardrop, this fancy gem shape is rounded on one end and pointed on the other.

An optical effect which appears in certain gemstone materials. Often revealed by or enhanced by proper fashioning.

A continuing glow exhibited by some gemstones after the source of illumination has been removed.

Pigeon's Blood
Refers to the most prized color of red in rubies. Pigeon's blood red is thought to be a pure red with a hint of blue. It is associated most with rubies from Burma, though any ruby could be this color.

Play of Color
Prismatic flashes of color seen within a gemstone. The color display in Opal.

Change of colors observed in double-refractive gemstones when viewed different directions. Selective absorption and varying transmission rates of light cause the color change when the gemstone is viewed along different optical axes.

A gemstone unit of weight equal to 1/100 of a carat.

The smoothness of the surface of a fashioned gem in which optical reflection is maximized and shows no visible wheel or burn marks.

Portuguese Cut
The portuguese cut refers to a particular type of faceting where the gem is cut with two rows of rhomboidal and three rows of triangular facets above and below the girdle. The Portuguese cut thus has an extra row of facets on the crown, and this style enhances the brilliance of the gem. The Pportuguese cut is one of the most popular fancy cuts in the market and you'll find many varieties of gems cut in this style.

Precious (gemstone)
Traditionally, the four precious gemstones are diamond, ruby, sapphire and emerald. Today, the distinction between precious and semi-precious gems has been rejected by some gem trade associations.

A narrow tab of metal folded over the girdle of a gemstone to secure it in a setting.


Amethyst, citrine, chalcedony, and many other gems. Composed of silica and oxygen (SiO2).


Reconstructed Stone
A man-made gemstone produced by fusing together small particles of a natural stone.

Light returned to the viewer after striking a surface without entering it.

The change of velocity and resulting bending of light as it passes from one medium into another medium of different optical character.

Refractive Index
The ratio of speed of light in air to its speed within a substance.

An instrument used to measure the degree of refraction with a gemstone. One of the primary tests to identify gemstone material.

Small, facetted beads often used as spacers in a string.

Uncut gemstone material.

The red variety of tourmaline, including the color range from pink to red.

Needle-like inclusions within stones. Sometimes producing a gem phenomena such as asterism (star) or cat's eye.


Saturation is one of three characteristics used to describe the appearance of color. Saturation (also known as intensity) refers to the brightness or vividness of a color. See also hue and tone.

Semi-precious (gemstone)
An outmoded term for gems other than diamond, emerald, sapphire, and ruby.

A gemstone cut in the form of a beetle.

The appearance of a floating, billowy light in cabochon gemstones or a stationary sheen on the flat surface of a stone. Seen in certain Feldspars such as Moonstone. Adularescence.

Reflections from a polished surface as its relative position to either the viewer or the source of illumination changes.

Carved or engraved ivory or vegetable ivory. The engraved lines and textured surfaces are often colored with inks and dyes.

A mounting or the portion of a mounting which actually holds the stone.

Gems are fashioned into many shapes, such as round, triangle, pear, oval, and many more.  A round shaped gem may be cut in any of several styles... for example, brilliant cut, or Portuguese cut.    

Ans effect resembling luster, and is caused by light reflection from inclusions or texture inside the gem. Luster is light reflected from the surface of the gem and sheen is reflection from inside the gemstone

Side Stone
Side stones are set around or beside the center stone in a jewelry setting.

Single Cut
A stone with seventeen facets or fewer.

Single Refraction
A Most gemstones are doubly refractive -- they have 2 refractive indices. Only a few gemstones have a single refractive index, specifically diamond, spinel and garnet. See also Birefringence.

A single stone in a simple setting. Compare Center Stone and Side Stone.

The term used to designate a family of gemstones. For example, corundum is a species that contains the varieties sapphire and ruby. The Quartz family contains amethyst, citrine, and chalcedony, to name a few

Specific Gravity

The ability of a gemstone to resist deterioration.

Star Stone
A gemstone in which the phenomenon of asterism is visible as four or more rays.

Irregularity in the ordered structure of the atoms in a crystal.

Glass containing a high amount of lead oxide and cut to simulate a gemstone. Named for its inventor Josef Strass.

A substance used to imitate a more valuable gemstone. The substitute substance may be natural or man-made.

Swiss Cut
A gem cut consisting of thirty-three facets.

A man-made gemstone that has nearly the same physical, optical and chemical properties of a natural gemstone. Lab-grown gemstone.


The horizontal flat surface on the crown of a facetted gemstone.

Tetragonal System
A crystal system which consists of three axes, two of equal length and perpendicular to one another, the third perpendicular to the plane of the others.

Tiffany Setting
A solitaire (single-stone) setting for a facetted stone consisting of six long, slender prongs.

The relative lightness or darkness of a color.

A substance that allows transmitted light to clearly pass through. Objects cannot be seen through a translucent substance.

A substance that allows transmitted light to clearly pass through. Objects can be seen through a transparent substance.

Treated Stone
A stone that has been heated, dyed, irradiated, or otherwise processed in  order to improve the color or the clarity. Also pertains to gems that have their surface fissures filled.

The transmission of three different colors in three different optical planes as light passes through a gemstone material. May be used to distinguish one gemstone material from others.

Triclinic System
A crystal system which consists of three axes, all of unequal lengths and at oblique angles to each other.

Trillion Cut
A faceted cut in a triangular shape with 44 facets.

A twenty-four sided geometric solid. One of the crystal forms of the Isometric crystal system.

Tube Setting
A bezel setting in which a bearing cut into the end of a tube.

Tulip Setting
A prong setting with a small base where it is attached to the body of the jewelry piece and usually has a peg on the base which is inserted into a hole for solder attachment.

Tumbled Stone
A gem with an irregular or baroque shape. Polished by random application of an abrasive material.


Ultrasonic Cleaner
A machine commonly used by jewelers to clean jewelry effectively.  The ultrasonic vibrations free most types of dirt, grime, and oils from the items. Some ultrasonic cleaners come with a heating unit.  When using this type of cleaner, extreme care is recommended because certain gems cannot withstand the heat and vibration.

Ultraviolet Light
Light that is invisible to the naked eye because it is emitted in wavelengths shorter than those of visible light

Uniaxial Stone
A gemstone possessing one optical axis. Crystals of the hexagonal or tetragonal system are uniaxial.


Vegetable Ivory
Any hard, white or cream-colored product of a plant which simulates elephant ivory. It has gained in popularity as the harvesting of animal has been banned or severely limited.

A term referring to the luster of a gemstone. Gemstones with a vitreous or glassy luster are by far the most common in the gems world.


One of the technical terms used to refer to the luster of a gemstone. Turquoise is an example of a gem with a waxy luster.

In a well cut faceted gem, the pavilion facets (those on the lower half of the stone) should reflect light back out the top or table of the stone. If the facets are cut below the critical angle for the particular material, light will pass right through the stone instead of being reflected back towards your eye. When this happens the gem will lack sparkle and brilliance


Characteristic of wood. In jewelry the term is applied to petrified wood. (I really had to wrack my brain on this one.)


A synthetic gem... yttrium aluminum garnet.. 


Zirconium silicate. Gem zircon occurs in many colors.

(color zoning) A term that describes the uneven distribution of color in a gemstone. Zoning is best seen when looking at the stone through the table facet.

This gemstone and diamond dictionary will be developed into an easily accessed page on this site.

Enter any of the keywords defined above into the search box below to find related resources.




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Gem Industry News...


Zimbabwe Diamond Fields


The diamond fields of Zimbabwe are the scene of many human rights abuse reports, according to diamond trade news reports..

Over the past couple of years Zimbabwe has experienced horrific political conflict and massive economic inflation that has totally destroyed the value of the country's money. 

I'm told that this environment has contributed to harsher worker conditions and government regulations.

The international diamond community is threatening sanctions on Zimbabwe's ability to participate in the diamond market because of these abuses..

Our friend Bill lives in Zimbabwe, where he is a farmer, safari guide, and colored gem cutter. He states that he hears that conditions in the diamond fields are bad, but he doesn't go near those places.

He hears this from people that come looking for work. He doesn't have work for all of them... but he looks the other way when they sneak into his fields at night to eat his tomatoes and such.


gemstone news


Jewelry Dealers


An ailing economy is an opportunity for independent jewelry dealers.

People still want and need jewelry. Gift occasions, people building and refreshing their wardrobe, and see it - like it - buy it purchases are all sales opportunities for you.

An ailing economy isn't a deal killer when you offer quality, service, and low prices.

Be The Quality Jewelry Discounter.



gemstone news


Jewelry Dealers Program

Do you enjoy jewelry and gems?sapphire ring

Do you enjoy talking with friends and co-workers?

Could you use an extra income source?

Take a look at our great Jewelry Dealers Program.



Carolyn Doyle

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