Jewelry Glossary - I

• Inclusions
  Irregularities, usually of foreign material, enclosed within gem materials, such as liquid- or gas-filled tubes, feathers, flakes, needles, crystals, etc.
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• Index Wheel
  Disc which regulates the stone setting on a facet head.
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• Inlay
  Positioning a gem material pattern in recessed soft material such as slate. Also inserting a stone design in metal.
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• Intaglio
  A gem engraving similar to a cameo but concave instead of convex.
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• Intarsia
  A gemstone picture made up of many precisely shaped pieces of material fitted together on a base of stone or wood. Also Florentine mosaic or pietra dura.
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• Investment
  A plaster-like material which is mixed with water and poured around the model to be cast in the casting flask. Also called cristobalite.
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• Iridescence
  A changeable multi-colored effect in gem materials such as spectolite, caused by light interference.
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