Absorption spectrum
It is the absorbed light in a gem or mineral when bands of light passes through. Different gems have different absorption spectra. All are unique about which colours are absorbed and which pass through. This plays a major role in identifying gems and it is easily distinguished between imitation gems to the real precious stone. To determine the absorption spectra of a mineral, a spectroscope is used.

 

Absolute hardness
It is a scale to measure the hardness of a mineral. It is used by scientists as it has its numbers in proportion. Mineral collectors measure hardness using the Mohs scale.

 

Artificial stone
A look alike gem material which is either a manmade imitation or synthetic.

 

Baguette
It is a rectangular style of a step cut and used for small gem materials.

 

Baroque
It is a term used for irregular in shape, like baroque pearls, tumble-polished stones, or freedom shaped gem materials.

 

Blemish
It is a term used to any surface imperfection on the surface of a gemstone. As for example of a diamond, one would be referring to a nick, knot, scratch, abrasion, minor crack or fissure (cavity), or a poor polish.

 

Brilliance
It is the term used for the total amount of white light returned to the eye from a diamond or any coloured stone as the result of internal and external reflections. The factors which affect the amount of brilliancy in a gem are the refractive index, proportions, polish and transparency.

 

Brilliant cut
It is the most common style of diamond and many other gemstones cutting that consists of a combination of triangular and kite shaped facets. There are 57 or 58 facets in a round brilliant cut.

 

Carat
It is a unit of metric measurement used for gems. It is abbreviated with 'ct.' One carat is equal to 100 points, 200 milligrams, 1/5 of a gram.

 

Clarity grade
Diamonds are ranked on a scale from flawless, which is no inclusions visible under 10 x magnification, to included i.e. eye visible inclusions. Clarity grade is one of the four “C”, value factors.

 

Cameo
It is a carved gem or shell where the outer layers are cut away in such a way that the design stands out in relief against a background of a different colour.

 

Canary
It is a term which refers to diamonds with an intense yellow hue. If the yellow make the stone very distinctive, then the term "fancy yellow" is also often used.

 

Carbon spots
It is a black-appearing inclusions in diamonds, which is caused by the addition of graphite or homblende minerals.

 

Clarity enhanced
It is also sometimes called "fracture filled." It is a term used for a gemstone which has been treated for the improvement of its appearance by filling fissures or fractures with a transparent substance.

 

Diamond
It is a mineral which crystallizes in the cubic system and is composed of carbon with a hardness of 10 on Mohs scale (also see Mohs scale). Its refractive index is 2.417 and specific gravity, 3.52.

 

Dispersion
It is a term used for the separation of white light into its component spectral colours (also see fire).

 

Doublet
There are many gem fakes, one of them is this. In it a thin, flat section of a real gem is pasted atop a thick base of glass or rock crystal.

 

Emerald
It is the green colour beryl and among gemstone it is one of the most valuable one.

 

Emerald cut
It is a style of cutting a gemstone where the outline is of rectangular shape with cut corners and the shape of the facets are rectangular and trapezoid.

 

Four C's
It is cut, colour, clarity, and carat weight. This phrase is used to describe a diamond's value characteristics.

 

Fire
It is the flashes of spectral colours which are seen in a gemstone as a result of dispersion.

 

Flaw
It is an inclusion or a crack in gemstones which generally demotes its value.

 

Fluorescence
It is the process of a material which emits visible light when it is subject to ultraviolet light. As an example, diamonds under UV light often emits a visible light of a blue hue.

 

Fracture
It is a break within a gemstone.

Full cut diamond
It is a description of a brilliant cut, a round stone with 57 to 58 facets.

 

Gem or Gemstone
It is a precious or semi-precious stone that is cut and polished for the use in jewellery.

 

Gemology
It is the science and procedures being involved in mining, faceting, and also marketing of gemstones.

 

Gemmologist
It is a term for an individual who is practicing in the subject of gemology.

Girdle
It is the narrow band around the widest part of a polished or faceted gemstone, which divides the crown and pavilion facets.

 

High polish
It is a surface which has been polished to a mirror-like finish.

 

Hardness

It is the ability of a gem to resist scratching.

 

Inclusion
It is the internal characteristics present in gemstones. The common inclusions in diamond includes feathers, crystals, fractures, graining, pinpoints, cavities, etc.

 

Luster
It is the quality of the reflected and refracted light from the surface of a gemstone or pearl.

 

Marquise
It is a term used for the fashioning style for gemstones which has the girdle outline in an elliptical shape with pointed ends.

 

Mohs scale
It is a loose scale of hardness devised by a German mineralogist, Friedrich Mohs in the 19th century. It is used for field collecting, which allows for identification of specimens. The comparative scale of hardness is as follows:
1) talc
2) gypsum
3) calcite
4) fluorite
5) apatite
6) moonstone
7) quartz
8) topaz and beryl
9) corundum
10) diamond

 

Oval cut
It is a fashioning style for gemstones which has the girdle outline in an elliptical or oval shape.

 

Pavilion
It is that portion of a faceted diamond or any other gem material which lies below the girdle.

 

Pear shaped cut
It is the fashioning style for gemstones with the girdle outline in the shape of a tear drop or pear.

 

Point
It is a measurement in the weight of a diamond. One point is equal to 1/100 of a carat. Hence, 0.50 carats is equal to 50 points.

 

Polish
It is the smoothness of the surface of a fashioned gem. On it the optical reflection is maximized and it shows no visible wheel or burn marks.

 

Precious stones
It is rare and costly gems like diamonds, emeralds, sapphires, and rubies.

 

Princess cut
It is a modification of a brilliant square-cut gemstone. It is generally square-shaped in diamonds.

 

Radiant cut
It is a type of cut which is usually found in diamonds.

 

Refraction
It is the change in the direction of a ray of light which enters a gemstone.

 

Simulated stones
It is any substance which is fashioned to imitate the appearance of a gemstone.

 

Single cut
It is a brilliant round cut which has 17 or 18 facets: 8 bezel, 8 pavilions, a table and a culet facet.

 

Step-cut
It is a type of gem cut with a varying number of sloping parallel rows of four-sided facets which give the impression of harder.

 

Symmetry
It is a term used to refer to the quality of the fashioning of a gemstone. In symmetry grade the consideration is the balance of the outline shape and the precision of the facet arrangement.

 

Table
It is the horizontal and top flat facet on the crown of a faceted gemstone. The percentage of the table is a comparison of the table facet size to that of the width of the stone at the girdle.

 

Ultraviolet light
It is the light that is invisible to the naked eye as it consists of shorter wavelengths than those of visible light.