• Diamond - 0.999 percent crystalline carbon.

  • Die Casting - casting in a metal mold.

  • Dispersion - the spreading and separating of white light into its spectral colors as it passes through a gemstone. Another name for dispersion commonly used is fire.

  • Durability - the combined characteristics of hardness, toughness and stability of gemstones.

  • Dwtabbreviation for pennyweight.  A unit of mass which is the same as 24 grains, 1/240th of a troy pound or approximately 1.555 grams.