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Whether it’s understanding gemological or jewelry terms in an article you’re reading or simply gaining a greater understanding of the world of jewelry and gemstones, our Jewelry & Gem Dictionary is a handy reference guide. And, unlike most dictionaries, ours makes for interesting reading all on its own!

IGL
The Independent Gemological Laboratories, Inc. or IGL. This group is recognized by the jewelry industry as an authority for grading gemstones.

IMPERIAL JADE
Imperial jade is another name for emerald jade. It is a fine emerald-green color.

IMPERIAL TOPAZ
Imperial topaz is golden orange-yellow topaz; it is the most valuable type of topaz.

IMPERIAL MEXICAN JADE
Imperial Mexican jade is not jade at all; it is calcite that has been dyed green.

INCA EMERALD
Inca emerald is an emerald that is mined in Equador.

INCLUSION
An inclusion is a particle of foreign matter contained within a mineral. Inclusions can be solid, liquid, or gaseous. Many inclusions decrease the value of a stone, but some, like rutile forming asterisms in star sapphires and needles in rutilated quartz and tourmalinated quartz, are prized.

INDIAN AGATE
Indian agate is another term for moss agate.

INDICOLITE
Indicolite is a green to blue-green variety of tourmaline.

INLAY
An inlay is a piece of material (often stone or glass) that is partially embedded in another material (usually metal) such that the two materials make a level surface.

INTAGLIO
Intaglio is a method of decoration in which a design is cut into the surface. Signet rings are frequently decorated with intaglio, as are seals.

INTERGROWN
Intergrown crystals occur when two mineral crystals grow together and become one.

INVERALL SAPPHIRE
Inverall sapphires are a type of sapphire from Inverall, New South Wales.

INVESTMENT COMPOUND
An investment compound is a refractory material (it can withstand extreme heat) which is slightly porous (so that gases from molten metal can escape) and can be formed into a mold (which will be used in metal casting). An example of an investment compound is plaster of paris mixed with silica, boric acid, and graphite.

INVISIBLE NECKLACE
An invisible (or floater) necklace looks as though the beads are simply floating on the skin; the beads or pearls are strung far apart from one another on an almost invisible string (like clear fishing line).

IOLITE
Iolite, also known an water sapphire, is a transparent, violet-blue, light blue, or yellow-gray mineral. Iolite is pleochroic; a single stone will show many colors (in the case of Iolite, violet-blue, light blue, and yellow-gray). Iolite is not rare and has a hardness of 7 – 7.5. Iolite is found in Sri Lanka, India, Madagascar and Burma.

IRIDESCENT
An iridescent object displays many lustrous, changing colors. Iridescence is caused by the reflection of light from the jewel.

IRIDIUM
Iridium is a metal related to platinum. Iridium and platinum are frequently alloyed together, since the iridium increases the workability of the platinum. Iridium is also used for the points of gold-nibbed pens.

IRRADIATED DIAMONDS
Irradiated diamonds are diamonds that have been exposed to radiation. This changes the diamond’s color (as the radiation changes the crystalline structure of the diamond). The change in the diamond is permanent. Older radiation treatments involving exposing the stone to radium; newer treatments bombard the stone with atomic particles in a cyclotron (which accelerates protons, neutrons, or alpha-partices to high speeds). The irradiated stones take on a greenish or an aquamarine hue. Irradiations of diamonds was first done in 1904 by Sir William Crookes, who exposed diamonds to radium, giving them a permanent greenish color; his diamonds are still slightly radioactive (at the level of radium-painted watch). Newer irradiation techniques bombard the crystal with atomic particles in a cyclotron, and then the stone is heated to about 800 degrees Centigrade, producing a stone with very little radioactivity and a permanent color change.

IRRADIATION
Irradiation is the act of being exposed to radiation. Many stones (like kunzite) are irradiated in order to enhance their color. Being irradiated changes the crystal structure of the mineral by moving electrons. Irradiation techniques bombard the crystal with high-energy radiation (like gamma rays), producing a stone with very little radioactivity and a change of color. Some color changes caused by Irradiation are permanent, others care unstable and be reversed by heating or exposure to sunlight. For example, colorless topaz changes to a cinnamon brown color after ibeing irradiated with cobalt-60 radiation, but the color fades as the stone is exposed to sunlight. A new method of irradiation changes clear topaz to a brilliant, non-fading blue.

ITALIAN LAPIS
Italian lapis is not lapis; it is actually blue-dyed jasper from Italy.

IVORY
Ivory is elephant tusks (the large, upper incisor teeth), which used to be carved into beautiful jewelry, trinkets, and piano keys. The finest ivory is the white African elephant ivory; Asian elephant ivory is yellower. Ivory has a complex characteristic grain which helps distinguish it from imitations. Using ivory is now banned since elephants are in danger of going extinct. Other tusk-like material is often substituted for ivory, including walrus tusks, whale teeth, hippopotamus teeth, animal bone, palm seed, and more recently, plastics. Vegetable ivory comes from the inner seed of the South American ivory palm and was used for small items, like dice. Synthetic ivory is made from plastics (like celluloid) and is called “French Ivory,” Ivoride, Ivorine, or “Genuine French Ivory.”

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