Alexandrite

A variety of Chrysoberyl; Mohs’ 8.5 (hard & tough); yellowish-brown to green.

Known for cat’s eye (chatoyancy – due to light reflecting off needle like inclusions) best seen in greenish-yellow cloudy stones due to inclusions responsible for the optical effect – sometimes referred to as cymophane.

First discovered Ural mountains, Russia, 1830 and named after Czar Alex. II. Other sources inc Sri L., Myanmar, Tanzania, Madagascar, Zimbabwe, India.

Specific locations show slight colour difference. Brazilian – purplish red and blue hues; Sri Lanka – more olive green.

Mainly known for colour change properties – green in the day and red in incandescent indoor light. Colour effect, when seen in other gems is referred to as the ‘Alexandrite effect’. Alex with good colour change is highly desirable esp if large and with good clarity. Even rarer is when they have colour change & cat’s eye.

Can grow in a lab and is imitate by colour change, synthetic sapphire.