Hardness

Mineral's resistance to scratching on a smooth surface. Mohs scale of relative hardness consists of 10 minerals, each scratching all those below it in scale and being scratched by all those above it.

Hearts and Arrows

A general term when referring to diamonds with a percise and complete pattern of hearts and arrows achieved by perfect cutting proportions.

Highest Price

There are various ways of considering the highest price paid for a diamond, total price, per carat price, and relative price in today's money. We will be adding a highest priced diamond page.

Hue

Pure, spectral (prismatic) color. Hues include gradations and mixtures of red, organdy, yellow, green, blue, violet and purple.

IGI, I.G.I., International Gem Laboratory

Organization with laboratories located in the heart of the gem & jewelry districts throughout the world, including New York, Antwerp, Mumbai, Bangkok and Tokyo.

Ideal Cut

Theoretically perfect cutting proportions for (round brilliant cut) diamonds. Exact specifications vary. Many mathematical models ignore girdle thickness.

Imitation

Anything other than diamond which imitates diamond. Other words used include simulant and fake. It is important to note that synthetic diamond is real diamond. An imitation can be natural or synthetic.

Incomparable

A large diamond weighing 890 carats in its rough state, 407.48 carats polished, the third largest diamond ever cut.

Incident Ray

The name of a ray of light as it enters a diamond, or change of medium.

Integrity

Integrity is important in most business to business markets, and the commercial diamond market is said to operate with integrity. Some proponents of the Kimberley Process speak about the integrity of diamond itself, as though this had ever been questioned.

Internally Flawless ( IF )

A clarity grade which allows for naturals or other surface features or imperfections.

I.D.M.A.

The International Diamond Manufacturers' Association was formed at the end of World War II, and first met in Antwerp in 1946.

Included Crystal

A mineral crystal contained in a diamond. Inclusion: Imperfection internal to the Diamond.

Internal Graining

Internal indications of irregular crystal growth. May appear milky, like faint lines or streaks, or may be colored or reflective.

Irradiated Diamond

A diamond which has been exposed to radiation.

Isomer

Diamond is one of the isomers of carbon. Isomers are molecules which have the same molecular formulae but different molecular structures.

Jade

A description of the color of certain green diamonds.

Jewellery

Diamonds are not necessarily jewellery, and vice versa, but diamond jewellery accounts for the bulk of diamond demand and sales by value, and is an important section of the jewellery market.

Jubilee

A shape of diamond cut with 8- facets. A large (245 carats) and famous diamond, originally called the Reitz diamond. Renamed when it was recut in 1897 during Queen Victoria's diamond jubilee year.

Laser Drilling

A diamond enhancement technique whereby a laser is used to drill to an inclusion which is then bleached to enhance the diamond’s appearance.

Laser Drill Hole

A tiny tube created in a diamond by laser drilling, which is often done to treat diamonds.

Loupe

A small magnifying lens used to examine diamonds. 10x magnification is the standard.

Loupe Clean

Indicating that a diamond contains no visible inclusions when using the industry standard magnification of ten times (10x).

Lower-Girdle Facet

The facets on the pavilion of a round brilliant just below the girdle.

Luster

The luster of a diamond is its highly reflective surface sheen due to its high refractive index combined with the highly polished surfaces.