The aspect of the appearance of a material that seems to emit or reveal tiny bright points of light that are strikingly brighter than their immediate sur round and are made more apparent when a minimum of one of the contributors (observer, specimen, light source) is moved.

(For gonioapparent coatings) the per ceived contrast of the light/dark irregular pattern exhibited when viewed under diffuse illumination, scale typically <100 μm. JTC 12 (D2/D1/D8): THE MEASUREMENT OF SPARKLE AND GRAININESS