A form of heat treatment which affects the color of sapphire by adding the element beryllium to the heating process. Beryllium 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 sapphires can be produced from weak yellow or greenish gemstones.
The intensity of the internal and external reflections of white light, which are returned to the eye through the crown of a gemstone. Proportions, polish, symmetry, clarity and overall craftsmanship all affect a gemstone’s brilliance.
The standard unit of weight, not size, used for gemstones. One carat is equal to 0.2 grams. When talking about gold, on the other hand, the similar term (Karat) is used to describe its purity.
A term used to describe the relative absence of inclusions and blemishes in a gemstone. A gemstone’s clarity rating has a direct effect on a gemstone’s beauty and price.
Cut refers to the facet proportions on the surface of a gemstone, its polish and symmetry. More than any other factor, the precision of its facets determines the beauty of the stone.
The part of a gemstone above the girdle plane.
Small, octagonal facet on the lower point of the pavilion. Can be found for example in some brilliant cuts. _______________________________________________
Dispersion or Fire
Fire is the result of an optical property known as dispersion. The term is used to describe the rainbow-like flashes of color that are commonly seen in diamonds and other gemstones. Each color represents a wavelength within the spectrum of visible light – red, orange, yellow, green, blue, and violet. Fire is best seen in colorless or lightly colored gemstones, since deeper, richer colors tend to mask the effect.
Flat, polished surface on a cut gemstone.
The narrow band that circumscribes the edge of the plane intersecting the crown and pavilion of a gemstone. The girdle may be polished, faceted or bruted (rough surface).
Hardness – Mohs scale
The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals. The minerals are arranged from softest to hardest. Harder minerals, with higher numbers, can scratch those with a lower number. Diamonds are the hardest gemstone with a ranking of 10, the highest possible on the Mohs scale. The Mohs scale was created in 1812 by the German geologist and mineralogist Friedrich Mohs.
Any internal clarity characteristic of a gemstone. Large or numerous inclusions are considered flaws that seriously diminish the value of a gemstone.
The portion of a gemstone below the girdle, including the culet. _______________________________________________
Part of the metal setting designed to hold the gemstone in place. _______________________________________________
The amount a beam of light bends as it enters a gemstone and then strikes a subsequent surface(s) is known as the gemstone’s refractive index or RI. The amount of refraction depends on the structure of the stone. A gemstone’s RI is one of the most important characteristics that identify its brilliance.
Scintillation or Sparkle
The flashes of reflective light emanating from a gemstone’s polished facets are observed when either the gemstone or light source is moved.
Setting or Mounting
The metal structure which holds the gemstone in place. The design and workmanship of the setting is critical to the overall beauty of a jewelry piece.
The large facet in the center of the crown of a polished gemstone. On a round-brilliant-cut gemstone, the table is octagonal in shape.