It is an aluminate of beryllium – a mixture of aluminum and beryllium – having traces of oxide of iron and chromium, which serve as coloring agents and give it brownish and greenish tinges. It has a chatoyant glowing from inside like the eye of a cat and has white fibers. The brighter the fiber, the higher is the quality of the gem. Cat’s-eye has a silky streak of light that moves with the turning of the stone like a gleam in a straight line across the stone.