• Illusion Settinga setting in which the surrounding metal's surface is shaped or cut to appear to be part of a diamond. This type of setting is used to enhance the size of small diamonds.

  • Inclusion - a foreign body or irregularity within a gemstone.

  • Inlay - placing shaped pieces of material into the surface of an object so that both the material and object are level.  A popular type of inlay is different colors of opal set into jewelry. 

  • Intaglio - a design carved into or below the surface of an opaque gemstone such as black onyx.  This type of carving shows the image in relief.  It would be the opposite of a cameo. 

  • Nacre - (pronounced like acre) - a secretion by the mantle from certain mollusks.  It forms an iridescent layer on the surface inside the mollusk shell of both the pearl and mother-of-pearl.

  • Navette - a gemstone with pointed ends and having a boat shaped profile.  A good example would be the shape of a football.

  • Nickel - one of the eight transition metals which are mainly responsible for color in gemstones.

  • Noble Metals - a group of metallic elements which resist chemical action and do not tarnish in air or water (e.g. gold, platinum and the platinum group metals).

  • Nucleus - the core of a natural or cultured pearl.  This is the irritant which triggers the formation of the pearl.