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| Word |
Description |
| IGI |
Stands for the "International Gemological Institute". It is the largest independent gem certification and appraisal service in the United States. |
| Igneous |
A substance produced under conditions involving intense heat, such as that which is found in volcanoes. Igneous rock is rock formed by solidification from molten magma. |
| IMMAC |
hyperlative estimate of the general condition |
| Immob |
(remote) alarm/immobilizer |
| Imperial Standard |
Established throughout Great Britain in the Geo. IV Weights and Measure Act of 1824 with introduction delayed until 1 January 1826. This replaced the Old English Wine Standard (OEWS) and many other regional standards in the UK. The Act, of course, had no effect on America's use of the OEWS which continues in use to the present time. 1 Imperial Standard Gallon = 1.2 OEWS Gallon. |
| Inclusion |
A naturally occurring flaw, (feather, fracture, fissure, carbon spot, or cloud), within a diamond or other stone. The test for clarity looks for these flaws. |
| Indicolite |
Blue Tourmaline.
Tourmaline: A complex crystalline silicate occurring usually in three-sided or six-sided prisms terminated by rhombohedral or scalenohedral planes containing aluminum, boron, and other elements. Black tourmaline (schorl) is the most common variety, but there are also other varieties, as the blue (indicolite), red (rubellite), also green, brown, and white. The red and green varieties when transparent are valued as gems. Tourmaline can be found in more colors than any other stone and heat can also be applied to tourmalines to lighten, or enhance, the existing hue of the gem. |
| Ingot |
Metal cast into a bar or other shape. |
| Inlay |
A decorative technique in which part of the surface of a piece of jewelry, furniture, or ceramic is cut away and stone, mother of pearl, or some other substance is embedded into the hollowed-out area so that it is level with the surface of the piece. See also channel inlay. |
| Intaglio |
Italian for "carving", an Intaglio is a carved gem wherein the design is engraved or carved into the object so that it sits below the surface plane of the material, as opposed to a cameo in which the design is raised from it's background, in relief. This technique was often used for seals, which made a raised impression in wax used to seal a letter or authenticate a document. It was commonly attached to watch fobs, since the watch fob is a good manner of carrying a seal. Once seals fell out of common use, the intaglio tended to face out to the viewer rather than down as on a seal. Some of the most commonly found Victorian intaglios were carved in carnelian, an orange-brown variety of chalcedony. |
| Invisible Set |
A method of setting square gemstones side by side in two or more rows within a metal border or frame so that they are flush against one another with no metal separating them. |
| Iolite |
(also called dichroite or water sapphire). A silicate of alumina, iron, and magnesia which is usually violet-blue, but can be deep blue, light blue-gray, and yellow-white. Makes a beautiful transparent gemstone which is remarkable for its dichroism. |
| Iridescent |
A display of lustrous rainbow-like colors. The colors seen in an oil slick or mother of pearl are good examples of iridescence. Synonymous with "Pearlescent". |
| Iridium |
A metal of the platinum family often alloyed with platinum to improve workability. Pieces marked "80% Plat. 20% Irid" would indicate that the alloy is 80 % platinum and 20% iridium. |
| Iron |
The most common metallic element which usually appears dark brown, from oxidation or impurity, but when pure is silvery-white. Iron is found abundantly in nature, usually in combined forms such as hematite, limonite, magnetite, and taconite. It is frequently alloyed in a wide range of important structural materials like cast iron, steel, and wrought iron. It is easily oxidized (rusted) by moisture, and is attacked by many corrosive agents. |
| Irradiation |
The process of bombarding a gemstone with X-rays, gamma rays or streams of subatomic particles in order to change the stone's color |
| Ivory |
A hard, smooth yellowish-white substance made from the tusks of elephants and walruses. |
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