Gemstones Terminology the Essentials Information You Need to Know

Shopping for gemstones can be confusing. Some of the gemstones terminology used in jewelry making can add to the confusion, because stones are labeled as natural, genuine, synthetic, simulated, treated -- or a combination of those terms. Yet, the more you know about the gemstone terminology used, the more money you can save.

That is why I put together this gemstones terminology glossary to help you understand the new terms used in the art of making jewelry.

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

• Adularescence or the moonstone effect: The shimmering light or whitish opalescence which glides over the surface of some gems such as moonstone. Interference phenomena of the layered structure is the cause of this effect.
  

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

• Asterism or star effect: Usually found in rubies, sapphires and block sapphires. This effect is caused by light reflecting off the needle inclusions that grow at angles from one another.
  

• Aventurescence or Schiller: A spangled, glittery effect caused by the light reflecting off of flat crystals inside a gemstone. This effect is usually found on aventurine quartz and sunstone.
  

• Baguette: A long rectangular gemstone shape, somewhat similar in shape to a loaf of French bread, hence the name.
  

• Blemish: An imperfection found in stones, it can be a scratch, a chip, or a fracture usually found on the surface.
  

• Body Color: The dominant hue within the gemstone.
  

• Bi-color: A gemstone exhibiting two color zones, such as ametrine or many tourmalines.
  

• Brilliance :The reflection and refraction of light displayed through a stone. Brilliance is sometimes referred to as "internal luster" to distinguish it from surface luster.
  

• Briolette: A tear or pear-shaped stone cut in triangular facets.
  

• Cabochon Cut: A gem that is cut round without facets into the shape of a smooth polished dome. This style of cutting is more often used for translucent or opaque stones.


• Calibrated: 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.
  

• Cameo: A gemstone cutting style in which a design or image israised above the surface of the stone. The most common cameos are made out of shell.
  

• Carat: A unit of weight for gems. A carat is one fifth of a gram (0.2g).
  

• Chatoyancy: The cat's eye effect sometimes seen in gemstones such as chrysoberyl, apatite and tourmaline is known by the technical name of chatoyancy.
  

  The effect is caused by tiny parallel inclusions that give the appearance of a narrow line similar to a cat's eye. Often a gemstone needs to be viewed in natural light to see the chatoyancy effect.
  

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

• Cleavage: The plane of weakness of some gems, where they will split apart with smooth surfaces. Gems with perfect cleavage are likely to break when being cut or faceted.
  

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

• Dispersion: The rainbow effect that’s visible when white light goes through a prism, bending and braking into colors of the spectrum.
  

• Dispersion: The property of a transparent stone to split light into the seven spectral colors, causing the "fire" which is refracted by the internal facets. Diamond has a very high dispersion, hence its high amount of fire.

• Double Refraction: The ability of most gems to split rays of light into two rays.
  

• Doublet: A doublet is a gemstone composed of valuable gemstone material in combination with other materials. It is found most often in opal, where an opal doublet contains a slice of opal glued to common opal, glass or other material. A triplet contains a slice of opal glued between a base and a crystal or a glass top. Triplets are usually less expensive than doublets, and both are less expensive than natural opals. Doublets may occasionally be found with sapphire or other expensive gemstones.
  

• Durability: the ability of a gem material to withstand wear. Durability is a combination of the gemstone’s hardness and toughness.
  

• Enhancement: Treating gemstone by different methods, other than cutting, to improve its color, clarity or durability.
  

• Fancy Cut: Sometimes used to refer to a gemstone cut in any shape other than the standard round cut, but also used to refer to gemstones that are cut in a shape other than the well known shapes of round, oval, pear, trillion, marquise, etc.
  

• Fire: The rainbow or colors that light rays form as they move through a gemstone. This is another word for "dispersion".
  

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

• Fluorescence: The ability of some gems to appear a different color when viewed under ultraviolet light. If or not a stone has fluorescence is a valuable aid in gem identification.
  

• Fracture Filling: Small cracks or fissures in a gemstone can interrupt the flow of light through the stone, creating white or "dead" spots in the color of the stone. Sometimes these fractures will be filled with 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.
  

• Girdle: The widest point in circumference of a gem. This is the point where a gem is usually held by fingers or tweezers for examination.
  

• 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.
  

• Hardness: A gem’s resistance to scratching.
  

• Heat Treatment: The application of high heat to a gemstone in order to improve its color and clarity.

• Hue: Refers to the position of a color on the color wheel, or 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.
  

• Inclusions: Foreign matter that is "included" within a stone. This may be a foreign body such as a crystal, a gas bubble or a pocket of liquid. There are many varieties of inclusions and they are important visual clues for identifying the type of gemstone and for identifying the origin of the stone.
  

• Imitation: A gem material that looks similar and is used in place of another more expensive material.


• Inclusion: Any foreign object or substance inside a mineral that is visible either to the unaided eye or with a magnifying glass.
  

• Intaglio: A type of gem carving in which the design or image is cut into a stone so that it is below the surface of the stone. It is the opposite of a Cameo.
  

• Iridescence: Effect caused by the interference of light on thin films within the gemstone.
  

• Irradiation: Exposing gemstones to radioactive rays from x-rays or other material to change or enhance the original color. Blue topaz is always irradiated, for example.
  

• Karat: 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.
  

• Lab created: Refers to gemstones created in a laboratory rather than by nature. A lab created gemstone is typically the same material chemically as its natural counterpart, as in the case of corundum produced by flame fusion or quartz grown using the hydrothermal method.
  

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

• Loupe Clean: A gemstone is said to be Loupe Clean when no inclusions or defects are visible when the gem is viewed with 10 times magnification.
  

• Luster: The outward appearance of a gem or organic material. The quantity and quality of light that is reflected from the surface of a stone. Luster is important especially when evaluating the quality of pearls.
  

• Marquise: The marquise shape is an elongated oval with points on both ends. Said to be named after the Marquise de Pompadour, the mistress of King Louis XV.
  

• 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.
  

• Mineral: An earth-building material made up of only one substance.
  

• Mohs Hardness Scale: Numerical scale ranging from 1 to 10 developed by Friedrich Mohs that assigns a rating to a gem according to its ability to resist scratching. The hardest is 10 (diamond) and the softest is 1 (talc).
  

• Moissanite: 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.
  

• Natural: A gem material that is found in nature. A natural stone can be treated in a variety of ways to alter their color or clarity. Natural is also the term applied to diamond blemish.
  

• Oiling: Oiling infuses colorless oils, resins or waxes into tiny surface-breaking fissures to hide them and give certain gemstones a cleaner 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 rather than oiled.
  

• Opaque: A term used for gemstones that you cannot see any light passing through the gem. Lapis and malachite are an example of this.
  

• Organic (gemstone): Most gemstones are minerals with a crystal structure but some gems, such as amber and pearl, are organic rather than mineral, being formed by plants and animals.
  

• Pavilion: The lower portion of a gemstone that begins just below the girdle.
  

  Pear Cut: Resembling a pear or teardrop, this fancy cut is rounded on one end and pointed on the other.



• Phenomenal Gems: Gems that display unusual optical properties such as color change, chatoyancy, asterism or iridescence.
  

• Pleochroism: The ability of certain gems to display two or more colors when viewed from different angles. This is a term also used for Dichroism and trichroism.


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

• Precious (gemstone): Traditionally, the four precious gemstones are diamond, ruby, sapphire and emerald. But other gems have also been labelled precious at times, including opal and amethyst. Today, the distinction between precious and semi-precious gems has been rejected by some gem trade associations. See also Semi-Precious gemstones.
  

• Refraction: The bending of light as it enters a medium and slows down.
  

• Refractive Index: A process using a refractometer to measure the speed and angle of light entering a gemstone. Very important for gem identification.
  

• Rough: In gemology, this refers to the raw, natural state in which gems are found, before they are cut.


• Rutiles: Needle-like inclusions (or foreign matter) within stones. These can produce some gem phenomena as an asterism (star) or cat's eye.
  

• Rubellite: Used to refer to the red variety of tourmaline, including the color range from pink to red. More of a marketing than a gemological term; these days gemologists tend to use simply "red tourmaline."
  

• Saturation: 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): Traditionally, the four precious gemstones are diamond, ruby, sapphire and emerald. Semi-precious gemstones include everything else. But other gems have also been labelled precious at times, including opal, amethyst and pearl. Today, the distinction between precious and semi-precious gems has been rejected by some gem trade associations. See also Precious gemstones.
  

• Sheen: This effect resembles 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: Stones with seventeen facets or fewer.


• Single Refraction: 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.
  

• Solitaire: A solitaire, often found in rings and pendants, is a single stone in a simple setting. Compare Center Stone and Side Stone.
  

• Species: 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.
  

• Synthetic (gemstone): A synthetic gemstone is man-made rather than mined from the earth. Natural gemstones which are treated by industry-accepted methods such as heat or irradiation are not classified as synthetic.
  

• Table: The flat top part of a gemstone. The table is the largest facet.
  

• Tone: One of 3 characteristics used to describe the appearance of color. Tone refers to the lightness or value of the lightness in a particular stone. See also Saturation and Hue.
  

• Translucent: A quality of a gemstone transmitting light imperfectly so that one cannot see through the stone clearly. Star sapphire is an example of this quality.
  

• Transparent: There are several ways a light travels through a stone. In a transparent stone, the light travels through stone with virtually no distortion. Transparent stones are clear and easy to see through. See also Translucent and Opaque.
  

• Treated stone: A stone that has been heated, dyed, irradiated, or stained in order to improve the color or the clarity. Also pertains to gems that have their cracks or fractures concealed by filling the material.
  

• Trichroism: A property of a stone that will show three colors or shades of the same color when the stone is viewed through a dichroscope.
  

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

• Vitreous: A technical 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.
  

• Waxy: 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.
  

• Window: 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.
  

• Zoning: 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 top table facet.

Knowing this basic meanings of gemstones terminology will help you learn to select the right stones. It can be overwhelming in the beginning as you are dealing with a lot of new information. Soon all the meanings of gemstones become natural part of your everyday jewerly making terminology.

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