The brilliance is as a quality characteristic of a gemstone using the more light from the stone in the direction of the viewer is refracted and reflected, the higher the brilliance. Special cuts result in selected directions in which a particularly bright, sharply focused beam falls. The stone then "sparkles" conspicuously as it moves.
Brilliance is divided into two aspects:
- Shine , external brilliance through direct reflection on the surface
- inner brilliance through reflection ( total reflection ) on the inner surfaces
A particularly brilliant stone is synthetic moissanite in brilliant cut , which even the most brilliant - so diamond brilliant-cut - surpasses and unlike the zirconia -Brillanten (Fianit, CSC) is harder to distinguish. The mineral with the highest brilliance is hematite (iron luster, specularite), which is also used as a gemstone, followed by the minerals cuprite (copper oxide) and rutile (titanium dioxide), which are more interesting for hobby grinders and which, due to their color, can hardly be confused with diamond are. Another highly brilliant stone is the Demantoid garnet variety .
In the case of gemstones, the cut proportions are decisive, which ensure the physical brilliance of the reflections, uncut material is often brilliant in its natural formation, but there are also gemstones that are by nature completely dull. The main measure of brilliance is the refractive index and double refractive index of the stone. The brilliance results from a well-chosen and highly precise cut that makes optimal use of the refractions in the stone. In addition, one also calculates the colorimetric brilliance , the amount of light reflected, i.e. the degree of reflection for the brilliance, to which the setting of the stone also contributes.
- Walter Schumann: Precious stones and gemstones. All species and varieties in the world. 1600 unique pieces . 13th revised and expanded edition. BLV Verlags-GmbH., Munich et al. 2002, ISBN 3-405-16332-3 , p. 38, 49 .