Ideal cut diamonds:
Basically, ideal cut diamonds are diamonds of a superior make that are cut to display optimum brilliance and dispersion. For a diamond to be considered ideal cut all the components (facets, table, crown, pavilion, etc.) must be cut to specific tolerances (angles and percentages). If not, brilliance and dispersion will suffer.

IGI:
International Gemological Institute. A laboratory which offers a grading report. IGI also produces written appraisals.

Imitations:
Stones that do not have the same chemical composition as the stones they resemble, and they may be made by nature or man. For example, red glass can be a man-made imitation for ruby. Garnets used to mimic rubies would be natural imitations.

Inclusion:
An inclusion within a gemstone is an internal flaw, or included crystal, bubble, cloud, graining, fracture, etc.. Inclusions are differnt from blemishs, which are imperfections at the surface of the gemstone. Inclusions are not always bad. Inclusions can be used like a finger print, to identify diamonds and other valuable gemstones. Inclusions can often be used to tell the difference between natural and synthetic gemstones, and in some types of gemstones, the inclusion can even pinpoint the source of the natural stone. In some cases, inclusions can actually increase the brilliance of a gemstone. A naturally-occurring imperfection in a diamond.
Some examples are: feathers, crystals, needles, clouds and pinpoints.

Invisible Setting:
The effect of this setting is of a brilliance unfettered by metal. In invisible setting, the stones are placed such that the metal is not visible from in-between stones. Invisible settings normally employ larger, square stones. Calibrated gems with slits are placed into a frame with ridges to hold them in place.

Karat:
Gold is a mixture of gold and other alloys. Karat is the measurement of gold purity.
(Also see 14k Gold, 18k Gold, 22k Gold, 24k Gold, Karat )

Length-To-Width Ratio:
A comparison of the length and width of the girdle outline on fancy-shaped diamonds. The ratio is found by dividing the length of the diamond by the width. The width is always stated as 1. Some L to W ratios are considered to be more appealing than others, but this is a matter of personal preference.
Pear 1.50 - 1.75 : 1
Marquise 1.75 - 2.25 : 1
Heart 0.98 - 1.02 : 1
Oval 1.33 - 1.66 : 1
Emerald 1.50 - 1.75 : 1
Radiant/Princess 0.95 - 1.05 : 1

Loupe:
A small magnifying lens, usually 10x magnification.

Marquise Cut:
A stone cut in a boat shape, pointed at both ends, with rounded sides. Note that the correct pronunciation is "Mar-KEYS", not "Mar-KEY" which is commonly heard.

Matte:
A non-shiny dull surface.

Mineral Crystal:
A tempered and hardened crystal that is scratch resistant. It keeps the watch looking like new for a long time and is virtually distortion free.

Mohs Scale:
A mineral scale based on 10 points, measuring hardness of the stone.

Omega:
A flat chain with a solid surface formed by the links and worn high on the neck.

Pavé Setting:
A setting in which small stones are set as close as possible, so that the piece literally looks 'paved' with stones. (pah-VAY) a gem setting technique in which the stones are set low and very closely spaced, so that the surface appears to be paved with gemstones. Most commonly seen with diamonds, but may be used with any stone.

Pavilion:
The lower part of the diamond below the girdle. On a round diamond it is cone-shaped.

Pendant:
An ornament suspended from a single chain.

Pierced Earrings:
Earrings designed for pierced ears. A wire or post is inserted through the ear lobe.

Platinum:
White precious metal used in jewelry settings or watch casings and watchbands. It is important to note that Platinum is not white gold. Platinum is naturally white whereas white gold is created from yellow gold by adding nickel, copper, zinc and sometimes silver. Platinum resists corrosion and does not tarnish. Platinum is harder than gold and silver, so it outwears them. Its hardness is about the same as Iron (4-4.5 on Mohs' hardness scale). Platinum is very heavy and dense compared to other metals. it is approximately twice as heavy as silver, and about 1.65 times heavier than 14k gold, and 1.4 times heavier than 18k gold. Because of its strength and density, Platinum holds diamonds very securely and has high resistance to wear. This is why Platinum prong settings are sometimes used on gold rings and why estate jewelry made of Platinum often looks relatively new after many years of wear. Platinum is very rare, even more so than gold. Over 20 times more gold and over 12.5 times more silver are produced annually. Approximately 95% of all Platinum supplies come from South Africa and Soviet Republics. Platinum normally cost more than pure gold on the monetary market exchanges. The high purity of Platinum jewelry (90%-95%) compared to 14k and 18k gold jewelry (58%-75%) is another reason why platinum is more expensive.

Polished surface:
A smooth and glossy surface, with no visible imperfections.

Precious Stones:
Gemstones such as diamonds, emeralds, rubies, sapphires, etc.

Premium Cut:
The brilliance of a diamond depends on proper cutting. premium cut to Ideal cut diamonds ensure that the diamond chosen will be as brilliant as it is beautiful. A diamond with these premium proportions will cost more but its brilliance is well worth the added investment.

Princess Cut:
Square-shaped gemstones.

Prong Setting:
The prong is the most popular gemstone setting. A prong is a narrow piece of metal that folds over the edge of the gemstone to secure it. A prong setting appears to elevate a stone higher than in other settings, and is used most often with diamond solitaires.

Quartz:
A crystalline mineral used for gems, including amethyst and rock crystal. Available in a variety of colors.

Quartz Movement:
An electronic movement in a watch powered by a battery that causes vibrations in a tiny piece of Quartz. This is the type of mechanism found in most watches.