The inclusion is hematite in aventurine quartz. Bleaching - is done on an organic substance like ivory and pearl that comes from nature with various discolorations. In a manner similar to removing clothing stains, gem dealers bleach these materials to whiten and improve their appearance. Bleaching is also used to lighten the body color of gems like the tiger-eye. Such enhancement intensifies its shimmering bands of color.
Golden coral is also the product of bleaching.
Poor-quality specimens of many stones that are usually faceted are often cut in this shape. Chatoyancy - an effect, which resembles the slit eye of a cat. This is caused by the reflection of light by parallel fibers, needles or channels. This phenomenon is most effective when the stone is cut into a cabochon in such a way that the base is parallel to the fibers. When the gem is rotated, the cat's eye glides over the surface.