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  • Dead - a diamond showing no lustre or brilliance as a result of heavy inclusions.
    A diamond showing no lustre or brilliance as a result of heavy inclusions (often clouds) can be described as dead. A dead stone holds far less value than a "clean" or lightly included diamond of similar proportions.
  • Depth -the height of the diamond.
    Measured from the top of the table to the bottom of the pavilion or culet.
  • Depth Percentage - depth (height) of the diamond divided by diameter (or average width).
  • Diamond - an allotrope of carbon (chemical symbol C).
    he hardness natural material known to man (10 on the Mohs hardness scale), diamond is also an excellent conductor of heat and, as such, is used in the manufacture of semi-conductors.
  • Diamond Gauge - also known as a "leverage gauge".
    his instrument measures a diamond's proportions to a 100th of a millimeter.
  • Diamond Grading Report - If you have a GIA, EGL USA or IGI grading report or certificate, then you can be almost certain you have a diamond. Certificates have been known to be forged, however.
  • Diamond or Fake? - an inclusion on the surface of the diamond where a piece of the diamond has broken off.
    This can be quite detrimental to the value of the diamond, as the diamond needs re-cutting to return it to its original state. This can lead to the diamond 'breaking its weight' (going below important or magic weight levels, such a 1.00 cts).
  • There are several ways to test a diamond:
    Use a diamond tester - this apparatus uses heat to see if the stone is diamond. Diamond dissipates heat very quickly, so this tool is very quick and effective;
    The "Dot" test - draw a dot on a piece of paper and place a loose diamond (table down, culet up) on the dot. If the dot is clear (visible), the stone is most likely a simulant, such as CZ. A diamond refracts the light and thus the dot should not be visible. Please note that some baguettes and marquises may still show the dot due to it
    Wear test - Diamonds are very strong and only wear or abrade when they clash with other diamonds. Simulants, such as CZ, on the other hand, are softer and abrade more easily. So, if you have a very worn stone (lots of little nicks and chip, especially around the culet and on the pavilion facets (leading down to the culet), then the chances are you have a stimulant.
    The "flash" test - again, with a loose stone, as you pivot the stone under light, the pavilion (underside) might flash orange over most facets (synthetic cubic zirconia) or blue and violet (yttrium aluminium garnet)
    Doubling" - when viewed under 10x magnification, synthetic moissanite, synthetic rutile and zircon will show "doubling." As you look through the table and rock the stone, the pavilion facet edges (underneath) and the culet will appear double (i.e. there are two of each of them). Diamonds are singly refractive, while moissanite is doubly refractive.