Glossary Of Terms

A cutting design of rectangular shape with sharp corners sometimes used as accent stones but can be used as a large center stone.

A surface characteristic on a gem generally caused by man via cutting, setting or wearing.

A style of cutting gemstones in which the crown and pavilion facets radiate outward from central point.

A trade term for a stone that has been heat treated.

Cabochons are gems fashioned with curved surfaces, dome shaped on top, with either a flat or rounded bottom.

The unit of weight (0.200 gram) used to weigh gemstones.

The effect where a gemstone changes colour in different types of light. ie: from green in daylight to red in candescent light.

A wonderful cats eye effect in certain cabochon gemstones resulting from light reflecting off fine needle like inclusions within the stone, seen as a straight line that moves across surface.

A clean gemstone refers to a gemstone which  does not appear to have any visible inclusions.

A ring suitable for formal occasions.

When two or more separate pieces of material are glued or fused together to form a single gem. The most common are made of two pieces and are called doublets.

The top part of a stone above the girdle.

The orderly three dimensional geometric arrangement of atoms / molecules in a mineral.

A small facet usually placed at the point where the pavilion facets meet.

Aa treatment process that uses a combination of high temperature and chemicals to enhance color or produces inclusions.

Durability refers to a gems ability to withstand ordinary wear. This is a conditional definition. It depends on the physical characteristics of the stone itself, the care it receives, who is wearing it and under what conditions and so forth.

Any human controlled process that improves the appearance, durability or value of a gem.

A small geometric face cut and polished on a gemstone to beautify a rough gemstone. These are usually cut in a systematic pattern designed to exhibit and emphasize the beauty of a gemstone

Partially healed internal fractures that literally look like a feather.

Flashes of spectral color overlying in a gems body color caused by dispersion.

A ring given to a friend to demonstrate the strength of feelings for them.

A certificate issued by gem testing laboratory on stones submitted for identification examples include: AGIS – IGS- GIA & AGI being just some.

A specialist in precious minerals, who studies gemstones from scientific and academic points of view. A gemologist must be able to identify precious minerals and provide an objective description of gemstone quality and value, adhering to strict professional ethics.

The thin line of cut stone that forms the boundary between the crown and pavilion, it is the widest part of the gemstone.

Hardness means how well the surface of a stone resists scratching. this is measured in the Mohs scale, which rates the relative hardness of gems from 1 softest like talc to 10 the hardest which is diamond. It is a myth that diamonds alone will scratch glass.

These refer to the description of colour. Hue is a color (such as yellow or blue) Intensity is the vividness of the hue and tone is the lightness or darkness of the hue.

Any type of material – natural or manmade- that looks like a gemstone and is sold as a look alike.

An internal characteristic (other than a fracture or cleavage) enclosed within a gemstone. These are not necessarily bad, as they may exhibit attractive characteristics and may also provide evidence of origin for gem identification purposes.

karat (K) refers to the fineness of pure gold content in proportion to the amount of alloy
(not to be confused with ‘carat’ the unit of weight for weighing gems).

24K = 100% pure gold stamped 950 where less visible on jewelry
14K = 58% pure gold -stamped 585
10K is 41% pure gold – stamped 416 

The lower part of the stone below the girdle.

The sharpness and appearance of a gems surface in reflected light.

Refraction is how much a gemstone slows down and bends light entering it.

The light bending capacity of a gem is expressed as the refractive index (RI). It is characteristic for each gemstone and effects the total amount of light the stone returns to the eye. Measuring the RI is a standard gemological test to identify gems.

An uncut gem that hasn’t been faceted yet.

A ring with one stone.

Refers to several properties including response to heat and temperature changes, 
radiation including light and chemicals which have a chance to harm a gemstone.

A reproduction of a natural gemstone, with essentially the same chemical composition and optical and physical characteristics as their natural counterparts.

The large facet at the top of the crown, usually the largest on the stone.

Toughness is resistance to breaking, chipping or cracking under mechanical stress. The toughness of any particular gemstone is dependent on the structure and composition of the material itself.

Transparency means how well a material passes light. Gemstones are classified from transparent to translucent to opaque.

Any process a gemstone is subjected to in an attempt to improve the color or clarity. The most common forms of treatment are heat, chemicals radiation, oiling and dyeing.

A gemstone fluoresces if it glows when exposed to electromagnetic radiation (EM) and then stops when the radiation is cut off. Sunlight or even a bright filament source can cause fluorescence in some gems and modify the color we see.