White or silver-blue haze displayed by high quality moonstones and other gems.
Alluvial Deposits
Gem deposits found in water after they have been separated from the mother rock.
Oddly shaped pearls that form during cultivation.
Brilliant cut
A round shaped stone that has a minimum of fifty-eight facets.
Cabachon cut
The rounding of a gem without facets into the shape of a highly polished dome.
The art of carving a shell or similar material above its background.
A unit of weight for gems.
The ability of some gems to display a second color when viewed from a different angle.
The splitting of light as it enters a gemstone. Also called the stone’s “fire”.
The cut and polished part of a gemstone.
The rainbow or colors that come from light rays as they enter a gemstone.
A mineral or combination of minerals that display a high degree of beauty, rarity, durability and desireability.
A hollow rock cavity usually containing some form of one or more gemstones. Amethyst and Peridot are examples of gemstones found in geodes.
Heat Treatment
The application of heat to a gemstone for the purpose of improving its color.
Illusion Setting
Any setting that is not as it appears. This is often done by combining several small diamonds with rhodium to give the impression of a higher carat weight.
Foreign matter that occurs within a stone and displays a different color or effects from the rest of the stone.
The play of color in a gemstone resulting from inclusions.
Unit of measurement that indicates the quantity of fine gold in a piece of jewelry. This is always based on pure 24-karat gold, eg. 18 karate gold contains eighteen parts fine gold and six parts metal alloys.
A skilled craftsman who cuts and polishes gems to their finished state.
The outward appearance of a gem or organic material. Luster is important especially when evaluating the quality of pearl.
An inorganic element of the Earth of consistent atomic structure and chemical composition.
Mohs Hardness Scale
Numerical scale developed by Friedrich Mohs that assigns a rating to a gem according to its ability to resist scratching, the hardest being 10 and the softest being 1.
A variety of iridescence that is most often light blue in color.
Organic Gem
Matter that is not technically a gemstone, but is derived from animal or plant life. Organic gems include amber, coral, ivory, jet, pearl and tortoiseshell.
Pave (Pah-vay)
A jewelry setting whereby one prong is touching three or more stones. If not, it is classified as a cluster. The pave setting is popular with diamonds.
The lower portion of a gemstone that begins just below the girdle.
The bending of light as it enters a gemstone and slows down.
Refractive Index
A process developed by Willebrord Snell that incorporates a refractometer to measure the speed and angle of light as it enters a gemstone. It is used in gem identification.
A stone carving that shows the sacred scarab beetle in intricate detail. The ancient Egyptians revered the scarab as a symbol of the soul.
Secondary Deposit
A deposit of gems that has been worn away from its original site, usually by the effects of weather. An alluvial deposit is one example of a secondary deposit.
The flat top part of a gemstone.
Table Facet
Central facet on the table (or crown) of a gem or simulant.
In gemology this term is loosely used to describe long thin lines that occur on the surface of the gem. The black lines seen in turquoise or howlite are an example of veins