Terminology

Knowing how to describe the properties of gemstones and its interactions with light

also means using the correct terminology.

When you look at a gemstone, what do you see? The following are some important terms used to describe a gem’s visual appearance as it interacts with light:"


  • Luster is the amount of light that is reflected from a gem’s surface.
    Onyx and its characteristic luster.

    Onyx and its characteristic luster.

  • Adamantine is the very bright and reflective luster displayed by Diamonds. It is derived from the Greek root word for Diamonds ‘adamas’, meaning ‘unconquerable’, which is certainly appropriate for the world’s hardest natural substance! Sub-adamantine is occasionally used to describe gems with a luster close to Diamond, such as Alexandrite and Demantoid. While there are other mineralogical terms to describe luster, these have been omitted because they are of little importance to your everyday appreciation of gemstones.
    Ambanja Demantoid

    Ambanja Demantoid

  • Scintillation is the play of light (reflections from a polished surface) that causes a gem to sparkle as its relative position to either the viewer or the source of illumination changes.
  • Brilliance is the amount of light (i.e. body color) that is reflected from a gem’s interior. Brilliance is dependent on a gem’s optical properties, cutting (critical angle), color, transparency, clarity, polish, luster and wear.
    Sphene and its fire

    Sphene and its fire

  • Fire also known as dispersion, is the splitting of light into its component colors. This gemological feature adds both beauty and value. While all gemstones of a large size exhibit fire, the most dispersive gemstones ranked in order are Sphene (Titanite), Demantoid, Diamond and Zircon.