Chrysoberyl Cat's Eye

Description :A translucent variety of chrysoberyl (beryllium aluminum oxide) which exhibits a silvery white line across the stone. This moves as the stone, the light source or the observer moves and may appear to open and close like an eye. The finest quality has a sharp eye that appears to open and close as the stone is rotated, and exhibits a strong "milk and honey" effect (stone on one side of the eye appears lighter than the other). These colours switch as the stone or light source is moved. The most highly prized body colours are greenish-yellow and brownish-yellow (honey colour).

Varieties Rare specimens also exhibit change of colour.

Sources Sri Lanka, Brazil. Phenomena Chatoyancy caused by the reflection of light off minute, parallel, needle-like rutile crystals or hollow tubes.

Hardness 8 1/2 Toughness Excellent Luster Silky Miscellaneous When a gem specimen exhibits both chatoyancy and change of colour, one or both phenomena will suffer. It is more common to find a good eye with poor change of colour. The conditions necessary for one phenomenon conflict with those needed for the other.

The term cat's eye when used alone refers to chrysoberyl. Other minerals exhibiting chatoyancy must be qualified, e.g. tourmaline cat's eye.

Other Distinguishing Properties Refractive Index -1.746-1.755

Specific Gravity -3.73

History Cat's eye has been regarded as a preserver of good fortune. The natives of Sri Lanka still consider it a charm against evil spirits. British royalty often use it as an engagement stone.

Cuts & Uses Must be cut in a cabochon to produce cat's eye effect. This should be cut so that the long portion of the cabochon is 90 degrees to the direction of the needles.